Holley Main Body Upgrade Question

I would work on tuning what you've got first before shelling out any money on new parts. Verify the mark(s) on your balancer, make sure you've got around 18* initial timing, or whatever the motor wants (if you add timing and the engine speed increases, it wants it), limit total mechanical advance to give to around 35* total (without vacuum adv hooked up), then start tuning the carb. Start with the float level and fuel pressure (if you have a regulator), then get the idle circuit working well (you may want to add a restrictor), then squirter and cam, main jets, power valve, that sec jets. Changes you make to the earlier items affect everything downstream.