Here's some ideas I had when designing my 273 that never happened. I wanted a street car plus able to do time attack. So I wanted around 400 hp with a nice flat powerband.
The reason I was gonna use the Ford valves is you get a decent aftermarket selection. I wanted the under cut ones to gain a little extra flow plus there smaller stems in the first place. And want valves big enough so the use a new part of the seat but not to much bigger than stock since its pretty tight in there even with notches. I also want to use beehive springs with tool steel retainers if I could get away way with it. I was trying to get away with the least spring pressure for the rpms I needed 7000-7500 But the car was also to be a street engine.
As for heads I used onewildcrazyguys@ flow numbers. I was gonna go custom cam. But found comps 268 solid roller work the best on my dyno program, probably the custom cam would be close to those specs. It had a pretty good powerband it peak hp around 420 @ 6700 rpm and 350 @ 5500 for torque. And started around 2500 rpm and didnt fall off much hp wise until 7500+ rpm. I know those are just desk top dyno but even if it came within 10% of those numbers I would of been happy.
As for your engine since your not gonna rpm so high you don't need solid but I'd still go with hydraulic roller. I think the trick to keeping a decent bottom end is to let the heads do most of the work with the least overlap you can get away with. So with roller you can get the lift and even 1.6 rockers might be a good idea to keep duraration down. And if you go with Rhoads roller lifters you can squeeze out a few more degrees may around 225-235 with or 215-225 without.
If not willing to port out I'd just notch and go with 1.94 magnum or EQ heads. Stock head will strangle the power unless your happy with under 300 hp. I'd be shooting for 350+ with your engine.
