Frame/data plate M3A1 0676w
The MFGRs No 676 provides the info that that was the 676th M3A1 made by Diamond T. It would have been accepted in Nov, 1943. The "W" indicates a Winch model. I think the USA Number assigned would have been 4063787, but it would help to get a few confirms off the real thing. It would appear that nearly the entire postwar inventory of the long, M3-ish HTs, as well as M16s were rounded up & converted to M16A1 & A2 in the early 50s. Any chance you could find the USA Number stamped on the bumper of either of those?
Frame/data plate 276576
The White MFRs Nos are so spread out on the M16s that they seem useless for even guessing date of acceptance or USA Number. Since you are fortunate enough to know the Ord Serial Number, & it is below S/N 1104, it provides the info that it was the 1040th M13 made by White, accepted May 1943. If it has an original White M16 dataplate in there, I think that would indicate that it was one of 568 M13s that White converted to M16 in Aug, 1943. Just from info the guys have provided, it would appear that these units retained their original M13 Ord S/Ns & Reg Numbers after the conversion.