This engine came stock with a Rochester Quadrajet 4 barrel. This will give you all around driveability & performance. Edelbrock makes a direct bolt on replacement carb for stock manifold applications that is great replacement.
Also use a holley 650 cfm with vacuum secondaries. be careful before you purchase a REPLACEMENT carb.... because 78 vettes only have so many inches between manifold and hood clearance for the stock air cleaner to be used.
PS...I own a 78 L82 Anniversary Edition...have been there done this before...Thanks Ned