You don't need big valves in a 318 streeter, for one thing.
And to make best use of premium fuel, you will need a final cranking cylinder pressure of around 160 psi, but to stay out of detonation with iron heads, no more than ~165psi.
The thing with alloy heads is, that you can run the pressure up to, in the range of 185 to 200psi. I run 180psi on 87E10.
Pressure is power, specifically at low-rpm. Which is what a longer-period cam always gives up.
Plus, when the bug for more power bites, the alloys will bolt right on to the biggest of small blocks; and you won't be stuck with the useless open chamber big-valve heads that you spent good money on.
IMO, with a 318streeter, you can sacrifice whatever you want to, so long as it ain't pressure.
Without the pressure, and WITH a bigger than stock cam; you will need a higher than stock stall and quite a bit more than 2.76 gears. I'll guess a 2800 and 3.23s at a minimum, up to 3.91s preferred..
The point is this; that altho the buy-in for the bigger cam is relatively small, the loss of pressure will end up costing more money.
But the even-bigger picture is that NONE of this makes any sense at all, breathing thru 273 logs and a single exhaust. If your engine has to pump it's own exhaust out, that costs power. And gas money
BTW-1
The Second generation Barracuda is the heaviest of the A-bodies of it's era. And that, on a 108" wheelbase, go figure. The folding rear seat is a tank, and the buckets/console is more fat. The heavy back glass is at least in the right spot.
To it's advantage are the very roomy rear wheel-wells. With a little work I installed 325/50-15s into mine; on alloy wheels of course cuz they weigh about half of the same-sized steel wheels.
Happy Hot-Rodding
