There are alot more options going with pre 86 aftermarket heads. it's not real clear what direction you're headed and it's not hard to tie up almost as much redoing iron heads as new aftermarket 180,,190, 195 cc. if you need valve, guides, machine work. Just imho, if staying flat tappet as retrofit is anything but budget, I stay away from Extreme, Voodoo, etc. fast rate cams, go for long lived instead of the 5 hp. A head manufacturer might say their springs are good for .550 but that doesn't mean they are right the spring pressure for the cam you pick. clearance and pressure are 2 different things/measurements. Old school, hard to beat a Comp 270 with Rhoads Lifters, 64 cc heads, 9+ C.R etc, does well with a stock converter but a 2.5k converter really helps it shine.. Spins 6k +, excellent, non finnicky drivability, and hard to destroy a 2 bolt block with it. Built it with and without 1.6 rockers @.501 lift but keeps it sub 218 @.050 duration several times. Pick a cam based on sound and you've almost 100% picked less performance. No, the 270 doesn't sound rat nasty, but it rev's super quick and you know something non stock is there....like a sleeper. Nothing exotic but runs surprisingly hard for what it is.