[xylorex]

Have you thought about upgrading to roller lifters? My 87 block had provisions in the lifter valley for the brackets even though it came with flat tappets.

You can also install the retro roller kits that work with untapped blocks, Ive done that before too.

Ive also installed a few Edelbrock pro Flo systems, when they fire up they either run or don't run in my experience.

Just my thoughts, good luck with your project!