What Fred said.
I made this swap recently. The clutch is different, the bellhousing is different. The motor mounts are different. I bought a tubular crossmember from Classic Parts for the engine mount.
I'm assuming you are changing the driveshaft, transmission and rear axle too. But I THINK the original transmission will mate to the 250 bellhousing. I changed tranny and rear axle, so I'm not sure about that.
One other thing. I wanted my bellhousing and transmission to mount in the exsisting holes on the original crossmember. I had to cut my firewall to get the 250 engine back far enough. the back of the head was hitting the firewall. Some of the other guys who have made this swap tell me they didn't have to modify the firewall. Click here for a photo.
http://i298.photobucket.com/albums/mm241/rickysahn/1952%20Chevy/01-20-09_1155.jpgBluedawg
