Proper Exhaust Diameter fo a 4bbl 225?

Here it is complete, valves and all. It's ready to bolt on. All I need to do is finish the short block.
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That is a real work of art.
I just finished catching up on SlantSix's thread on his 64 Dart project and am just gobsmacked at what some of you guys bring to the table. Now I'm slapping myself to stop thinking about replacing my 3 on the tree with a 5spd :eek:.