64 barracuda 273

Keep the 273. You have a fine forged bottom end and factory mechanical lifters. Put commando pistons and cam in the old girl and you will be making 5 more horsepower than a stock 318. Or put a d dart spec cam in her and you will be making 45 more horsepower than a 318. The 318 also never came with the sharp valve covers or air cleaner the little 273 did. A 273 is an excellent engine.