Offenhuaser dual port intake and Holley 550 on 318

the theory is a good one my experiences with them were on a 440 and the stock manifold made more power and mileage was even higher but i never tried to tune the carb when i put it on so there may something there too but on your 318 over a stock 2 barrel might be alright. the idea of the manifold is to keep air speed very high giving good throttle response and good economy at cruise or part throttle the same time giving you good 4 barrel hp ill just say this im not a fan of these manifolds but im with ya when you dont want to spend money and you have something laying around its like free beer you dont complain. id use it/at least try it... carb size sound fine