Shell Rotella T Triple Protection, 15W-40 Part# 550023277.
It has the zink in it, and its tech department bulletin recommends it for 1990 and older equipment with older style cam shafts.
A lot of guys use it in the G503 jeeps too. I have used it for about 10 years in my MVs. It is reasonably priced too, and available at most truck and auto parts suppliers locally.
I use the synthetic version in my 1967 John Deere 2020 for pushing snow in winter.
"Have fun with your jeep"
Jeep'in NY, About One Hour From Canada
42 GPW*42 M3 Halftrack*51 M38*52 M38A1*53M37
Vietnam Veterans of America unit 193
MVPA # 435
Member Niagara Military Vehicle Assoc; Ontario, Canada