Be on the lookout for one-piece (shown here) versus two-piece rear main seal engines. Chevy changed the crank seal in '86-and-later engines, which is a major improvement. Be aware that this will require a different flywheel/flexplate due to a smaller bolt pattern. Most one-piece seal engines came with provisions for a roller cam. However, a flat-tappet cam will still work in a roller block. One minor negative to one-piece blocks is that the gasket sets are more expensive.