Der Wolfshof: 8683jb and Mfrance are on track. I do not think this data plate is correct for the frame. Two separate vehicles. The Data plate is a post war rebuild plate. The plates were apparently produced by White Truck company but were used without concern on vehicles of any original manufacture. So this plate was affixed to a Autocar M3, Serial Number M3-22513 during February 1952 when that vehicle was converted to a M16A1. So no fold down armor and a taller M45 gun step ring.
The Frame Number 294254 would have been for a very late M16 built by White Truck Company around JAN 1944. Without the Ordnance number which is normally only found on the data plate we can only guess at more details. You might want to look in the three places most likely to have been stamped during a rebuild. 1. Top surface of the front bumper, 2. RH Bogie casting near exhaust tailpipe bracket. 3. LH Drivers door upper hinge.
Kevin