I was going to do the same exact swap. I have a '68 250 in my '52 2 ton now, so the bellhousing is the angle mount. The PO cobbled some junk to get it to bolt in, but that raised the trans up into the floor. I bought a crossmember from a '57 2 ton and will be swapping that in to get the bellhousing down where it belongs.
The original 4 speed trans is bolted to the bellhousing. I have no idea if it was modified or was a bolt in swap.
In checking on engine swaps, I decide to go with a 292 instead of a V8. I have the engine out being built right now. It will retain the original pistons but the head was shaved .030 and I have a cam and valve kit coming from Tom Lowe. He recommended the Clifford intake and I have that on the way. I also bought Hedman long tube headers from Streetside Auto and a Holley 390 cfm carb from Summit. Tom estimates the torque will be around 310 lbs ft. That is more than the 283 is capable of even with aftermarket parts.
You can build your 250 the same way and get almost as much torque out of it. Something to consider if you want more power.
I'd like to know more about the auxiliary trans you have and how it's mounted. I need to get more top speed without winding the engine to 5k with the 6.13 rear gear...
