As far as I know the trans is original. It still retains the drum parking brake and all original looking linkage. The trans is only a 1/4 inch from the crossmember. Obviously the bellhousing must have been changed from what I read about the 235's not bolting to a 250. Would the bellhousing mounts be located farther back than the 235 to move it all ahead this much ? I can see the rear mounts are probably the reason the trans sits too high. I'm assuming the originals bolted flat to the crossmember with maybe a piece of rubber between them. This has a tall rubber mount on a piece of the donor crossmember welded to the original.

1952 Chevrolet 6400 flat bed