I just had the same problem. The motor I put in my car had a SB 727. I am using a 999. I was able to marry the trans and engine and bolt the flex plate no problem. Once I put in the factory starter I found that the bearing backing the drive gear was hitting the flex plate by about 1/8". I went to my local auto part shop and compared a stock 727 and 904 flex plate and then I found out the 904 is about 3/4" smaller in diameter. I am to lazy to drop the trans so I bought a starter for a 98 Dakota. The Dakota starter is a mini starter and more importantly it has no bearing behind the drive gear. The back of the drive gear is webbed, so the drive gear stops itself from over throwing the converter. Hope this helps
