I have the adaptor you need for your munci 465. If you use the cummins adaptor for the gm transmission it is tilted 10 deg to the left looking at the back of the motor. They where done this way for clearance issues when they put the 4BT cummins in the bread trucks. I put a 4BT in my 85 gmc 1/2 ton and i did not want to tilt the engine or the transmission so i built my own adaptor. I have one on hand right now. It is all cnc machined and it works great. I have sold a few to guys doing 4 bt swaps. The 4bt is the same engine as your 12v just shy 2 cylenders. You need the adaptor and you need the cummins to gm flywheel. The flywheel is a little hard to come by used but you can get them new from Cummins. They are little harsh though they are about 900. 00 from what i have heard. If you are interested in the adaptor i have PM me and i will give you my number and i will fill you in some more on your swap. My 4bt has the 465 behind it.