I plan to backdate I Love Kit M923 A2 kit into an M923 plain jane. Could the tire sets from DEF Model be used? I though the rims and tires haven`t changed much over the years?
Yes, they are the same 11.00 x 20 tires and wheels.
The basic chassis, drivetrain, tires/wheels, and beds all remained the same between the M54 (M93 series), M809 series, and M939 series 6x6 5 ton trucks.
The big changes were new engines across all upgraded types. The engines are what give the A1, A2 subtypes.
Other type changes:
M809 series: longer hood length (to fit a larger engine), new grill, left side air cleaner, and larger NATO turn signals (also added to later M54s).
M939 series: new cab/hood, air brakes, and automatic transmission. M939A1 and A2 can also have the larger 14.00 x 20 super single tires.
Thanks Gino, I hope I can make the DEF Model parts fit to the ILK kit. 
I’m sure you can wrestle them into submission.
Based on the above differences and the way AFV Club has their parts laid out (M54 front hood, fenders, grill, air cleaner, etc. all on one sprue), I am hoping they also do an M809 series as well. It would be pretty easy for them. Fingers crossed.
AFV Club M54 front parts sprue.
I just ordered the ILK model. I hope it arrives before Easter. Let`s see how good the kit is.
Good deal. I am interested to see how the actual parts are as well. They look good in sprue-shots. The only part I am a little concerned about is the cab soft top being molded onto the cab shell. If you want to build it w/out the top, it could be an issue cleanly removing it. We shall see.
The model I have in mind has a hard top for cab and a canvas top on the cargo area. The latter will be a challenge to build from scratch.
Italeri made both a hard top for the cab and a canvas top for the cargo area in their various M939 kits. Whether they will fit on this new kit remains to be seen. They may be an option though.
I don`t think that the cargo area canvas will fit. Italeri cargo area is significantly too short and too narrow. 
I need to go tru my stash and see if I find the ancient Airmodel kit. I should have the right proportions since it was made from BMY references.
BTW can you post the pics of my sprues shots as soon as I have the ILK kit?
Sure, but can you not post from your end? You would need to email them to me or something.
If you want use plastic canvans I suggest you to cover its with umid tissue paper and vinilic glue