When converting to a dry element be sure to clean out the bottom sump, epoxy over any rust-through pinholes, clean and paint the inside of the air cleaner to prevent rusting!
Changing to a high flow paper element can certainly effect the mixture on a G503, heres why:
The WO carb on the G503 has an external bowl vent (Under the unsealed top air horn). Restrictions in the air cleaner system have more effect on such carbs' mixture control than more modern carbs with fuel bowls that vent into a sealed air cleaner horn, like a M38 YS carb. If the air filter is plugged, you will run richer. If you replace a restrictive/restricted oil bath filter, with a clean paper element, you will run leaner. The relatively high pressure present above the fuel in the float bowl vs the lower pressure through the venturi is what PUSHES the fuel through the jets. Any changes in this pressure ratio effects the mixture. The atmospheric pressure remains contant in the outside air, but it lowers above and below the venturi as the filter plugs up in any engine. A restricted air filter system with the WO carb will always have atmospheric pressure in the fuel bowl, due to the external bowl vent, but have an even lower air pressure in the carb from the restricted air filter, causing the richer running condition. The internal bowl vent of more modern carbs allows the fuel bowl to vent only to the filtered air stream, which if it's restricted, balances the difference in air pressure across the jet/s, keeping the fuel flow more constant as the filter plugs up.
Why change to a paper element?
An oil bath air filter is highly dependant on the air flow speed for it's efficiency. The main design of them is such that the air needs to make a 180* turn above the oil bath, which causes the majority of the dirt will keep going straight into the oil, the air will make the 180* turn. Too high of air flow speed, and the smaller particles will pull around with the air flow. too low of a speed, and the lighter particles won't have as much kinetic energy to fall out, also. The screening material in the element is meant to try to catch these fine particles that make it past the oil. The screen element is usually oil wetted to help retain these particles, but it is relatively coarse, which could let dirt through it, especially if the element dries out. The oil viscosity used in the sump effects the air filtering efficeincy, too. Too thick and the dirt can actually deflect off the surface tension of the oil, too thin, and it can be drawn up unto the air stream at high air flow rates. The oil viscosity is usually spelled out in the TM, for any given temperature range. Also, if the oil level is allowed to raise too high from the trapped dirt building up in the sump, and the vehicle is operated at odd angles, there is a chance that the dirty oil will be drawn into the engine. Dirt laden oil makes a very good lapping compound between the rings, pistons and the bores! Proper maintanence, per the TM is meant to minimize these issues. These procedures are messy and time consuming, and with oil at $5 a quart, getting expensive, too.
A major benefit of a modern paper element is it is a 100% filter, meaning ALL the air entering the engine is 100% filtered no matter what the air speed. the paper/fiber element has pores that are very fine, mechanically catching the particles larger than the pores, at any air flow speed. Oil wetting on the fine paper will trap even smaller particles than the pores. AC brand air filters many times are oil wetted paper. Late model Jeep elements are also oil wetted paper. All modern vehicles use this type filter because of it's cost effectiveness and filtering efficiency. Even M1 tanks use a paper element! Yes, they can plug up faster, and the elements do have some cost. Most an be cleaned at least a few times with a vacuum cleaner, but even if you simply replace it, the cost is alot less than the damage caused by dirt entering the engine. Some Jeep paper elements come with an outer layer of oil wetted foam to help trap the larger particles of dirt, with the oil wetted paper taking care of the fine filtering, without plugging up as fast. These are/were used on TJ Jeep Wranglers, and on older CJ and SJ V8s in the late '70s. Some '80s GM diesel trucks also had these dual filter elements.
Oil wetted "Cheese cloth" elements that are meant to replace paper elements can offer higher air flow and better performance as far as HP. The higher air flow rating comes from the more open spaces in the filtering media (Cheese cloth element). The oil saturated fibers in the cheese cloth act like the mesh element in the oil bath filter, relying on the dirt actually contacting one of the oil wetted fibers, and then sticking to it. A problem comes from the open spaces in the element not 100% effectively cleaning the air of dirt, and any excessive oil carrying fine dirt into the air stream, or if the element runs dry, the dirt does not stick at all. These filters do not filter the air properly, in my experience, to be considered for an engine that is operated off-road. I've seen a few modern Jeep engines worn out bores in 20k miles that are running these elements, with 1/2" layer of oily fine dust laying inside the intake manifold!. They only approach the filtering efficiency of a good paper element when they are nearly plugged up with dirt. One more issue is if the engine filter gets a good splash of water while fording, the water will pull oily dirt off the filter through the element and into the engine. The manual that comes with them states not to clean them for 50k miles, and the instructions for cleaning them should be followed to the letter. They are easily damaged by blowing them out with compressed air, and over oiling them will pull dirt into the engine. I do not recommend them.
Hope this adds to the discussion!
43 Ford GPW 92098
53 Dunbar Kapple M100
Sold: 61 CJ-5, 41 T207 WC-1 Dodge closed cab pickup
USMC Tanker (1811, 1812), 85-93
ASE Automotive Master tech, former Chrysler-Jeep Level 4 Mastertech, CA state EA smog license