wanting to convert 350 vortec to old school carb?

Check a Summit Racing catalog. They have carburetor heads for Vortec heads available for sale.

First you need to clarify if you have an LS Vortec or the original Small Vortec. GM makes aluminum four barrel intakes for each of these engines. No need to buy off-shore cylinder-head products from Summit.

Why go BACKWARDS?? Your Fi engine should be capable of more usable power than any carb could make. Engine with FI are more controllable and allow better breathing camshafts and better engine timing. There are other ways to improve your 350 than by going backwards to unreliable carburetion, that is imprecise and costlier to run. Makes no sense to me!