Posible swap for my 273 Barracuda 1966

There is a company called "spec" that makes a performance clutch for your 9 1/2" set-up. Search it for more info. I would say go with a well built LA 318 as it will work with everything you have now, oil pan, motor mounts, radiator, flywheel and you can use your forged 273 crankshaft. You should be able to build a street friendly 350 plus horsepower 318 without much trouble.