A properly set-up carb can take all kinds of boost.

A standard brass float carb, can take 5-7 psi of boost pressure?

I would not fill the floats, unless you cant find plastic floats.

My DCOE Webbers took about 5-8 PSI before the floats collapsed.

I then installed plastic floats & ran 9-10 PSI of boost pressure.

IIRC DCOE Webbers were good to about 12-15 PSI of boost range?

I like a stub stack instead of cutting off the horn, if you are talking about a Holley carb?
http://www.summitracing.com/parts/knn-85-0210?seid=srese1&gclid=CJS5hqW0uMQCFYc7aQodDI0AHQ

If you can, fuel injection is a better way to go over a carb.

MBHD

12 port SDS EFI