thanks for your help. i want to say that the ones that are mounted on the block already are a D2-AA and something else.....not sure because to be honest with you, this is my bro-in-laws engine and he's providing me with the info....he doesnt know for sure what's on there....he just removed his 428 cobrajet and is rebuilding a 390 for his 73 F100 to make it a daily driver.