Light pistons, strong light rods, well balanced crank (center counter weights on a V8) light weight, big bore short stroke, really good flowing heads, light weight valve train (narrow valve stems, titanium retainers, beehive springs), on a pushrod engine you tend to want very high rocker ratios so your lifter and PR can have shorter travel, intake and exhaust carefully tuned to an exact RPM range instead of off the shelf stuff, a shorter deck and/or higher cam position for shorter pushrods, meticulous oil control considerations, smaller bearing journals for lower bearing surface speeds, flat top pistons for best flame travel.