Originally Posted by 302 Z28
The one piece seal uses a crankshaft designed for the seal. You cannot use an older crank in a newer block. You can however use the newer crank in an older block with the GM one piece rear main seal modification kit. The one piece seal is a vast improvement in an area the small block Chevy has needed ever since it's inception. Rear main seal leaks are almost a thing of the past in the newer small blocks.
I don't know where you got this info from but I hate to tell you but you CAN use an older crank in a newer block and can not use a newer crank in a older block.
Think about it when those Bowtie blocks came out in 1986 we used a lot of older cranks in those blocks in the circle track engines we built back then.
We use quite a few of the newer blocks for the circle track engines we build and we use a different seal adaptor for using the older cranks in newere blocks.
Believe it or not here is a pic of a newer block with a older crank