AC ventura, as far as pilot bushing or bearing, I have used both without failures. I run bearing and grease them the lubriplate grease. Iron bushing I wouldn't use. Bronze bushing wearing out will do no damage to back of crankshaft. Bearing might. Before you put this assembly togeather, put the flywheel on the crankshaft and then the bellhousing and check for out of center. It's easier to do this measurement out side the car than inside. Close to ".001" in 12 oclock,3:00 , 6:00, and 9:00. I used extra long location pins. After having the bell housing centered I weld 2 nut on the bell housing that just clear the pins. This way you have the bellhousing centered on this block. There should be no wearing out of the bushing or bearing and last 100 k miles
Loctite all bolts and nuts except for the intake, water pump bolts, timing cover bolts, head bolts, and
oil pan. If you can get air craft nyloc nuts, use them where every possible. Good luck Rick