[Chris Hill]

Just curious, but when did Chevy do the following items on the small block?

1. One piece rear main seal
2. Flat tappet to roller tappets
3. Change intake manifold bolt patten on the middle bolts

The reason I'm asking is my father-in-law is repairing a 305 marine engine and the block is a one piece rear main seal with a flat tappet cam. I did not think they made those as the one piece seal and roller tappets were intoduced at the same time.

Thank you,