Is it stock 400. Most folks here will tell you to run the Quad. Better mileage and when done right equal or better performance than the others. I have had decent luck with Holley, but they are gas hogs. 5C heads will net around 7.6 to 1 not too good for performance, so do not bother with a huge carb. As far a vacuum you need to run the advance canister and the heater controls. Other than that keep what you want. Edelbrock performer intake will fit fine RPM will not. also Holley and E brock carbs will not fit air cleaner base either. Ram Air manifolds are great and do not cause clearance issues some headers will not allow reverse linkage.