I have a 74 F250 that has a 390 fe motor recently a wristpin has badly gouged the #8 cylinder. I am trying to determine weather to send the block to be boared and sleaved, or replace the 390 with a rebuilt 391 I have. I have read several other threads on this and the main issue I see is finding a flexplate to bolt to my recently rebuilt C6 transmission. I also thaught of changeing the crankshaft in the 391 with my 390 crankshaft would this solve the balanceing issue, or is a flexplate available for the 391 and where can I find one? Ford cannot find the part number c4tz-6375-f listed on another thread were the parts rights for the 391 sold with the Louisville line?