Found a set of rebuilt 97 351w heads with roller rockers for a reasonable price. Any reason I can't use these on an 85 block with non roller lifters and a flat tappet cam?

 

No reason at all.

 

And use the '85 pushrods.

 

Use the roller rockers too. But as for the springs, you'll need to have the pressure/installed heights checked to see if they're compatible with your cam. Roller springs are stiffer than flat tappet springs. Only if the cam is spec'd for stiffer springs (high performance grind) should they be compatible with your cam.

 

Cool. I heard the lifter bores in the roller blocks are bigger, just wanted to make sure there was nothing special with the heads.

 

Lifter bores are taller to accommodate the taller roller lifters, this doesn't affect anything running flat tappet lifters in them. All other dimensions of the blocks are the same