My knowledge of Vietnam armor is limited so please be gentle if this is a stupid question. From what I found the M548 was used to move and deliver ammo for the m107-109 spg. How hard or is it possible to convert the afv club m548a1 to the plan jane 548?

Not sure of the specifics for a conversion, but AFV Club kit AF35S32 is an M548 3-in-1, which can be built as a Vietnam version.

That's the kit k have been trying to find but no joy so I was getting to the point of buying the A1 a d back dating. That way as soon as I am done I can find the kit I really wanted.

The M548A1 had the same changes that the M113A2 had. Most of them are internal to the engine and transmission. The only real differences on the exterior deal with the suspension. The M548 had a lower rear idler wheel and shocks only on the first and last roadwheel. The M548A1 raised the rear idler wheel by a few inches (3mm in 1/35) and added a shock to the 2nd roadwheel from the front. Ther M548A1 upgades were made in the early '80s.

Here is a pic of the old Tamiya M577 (M113A1 base kit) where I added the A2 suspension features to it.

If your thinking of an initial m548, then the Tamiya M113 is your friend. It has the DeSoto 361 gas engine and the transmission that was only used a couple years. The running gear will be the same as well, but omit the water steer gear box and levers inside the driver's station. Remember you need the very first m113 kit from Tamiya
Gary
P.S. I never saw a gas engined 548 in Vietnam.

You can check out the instructions of the AFV Club kit to spot the detail differences between the variants :

https://www.1999.co.jp/eng/image/10049736

H.P.