13s and 15mpg Magnum head 360

This is a combo I drove for 3 years. even passed emissions in CT at the time. E body, 3.23 grip and 4sp.
shortblock first was a 340, then a 318, both used stock.
heads were X heads, Magnums would be a much better choice.
Intake was factory '71 Thermoquad. LD340 is a good intake, but I agree either drill the heads for LA intakes, or replace it with a Crosswind dual plane Air Gap style.
Comp Magnum 268H cam. (no XE then, but I dont think you need it with a 360 stroke anyway)
Matching Comp springs..I wouldnt ever run anything over .450 lift with factory springs. Why build in a rev limiter?
I ran a Thermoquad, and would use the one you have if it's in good shape and you know how to tune them. If not, I'd run the smaller vaccum secondary Holleys but again, carefully tune them...
You have a much lighter car, and I touched 13s even using the 318 shortblock with close to 1000lbs more.