A friend of mine had zoomies on his street rod; they were sort of a 'street zoomie' I guess you could say. They had what was essentially a cup with a hole drilled in the bottom; inserted in each pipe. Think like a spraypaint can top with a hole drilled in it.
T bucket guys have used motorcycle baffles in custom headers for years. They will burn out and need to be replaced so make sure you can remove and replace without much hassle.