292 stovebolt header exhaust issue

[cerial]

I have some stovebolt headers and have some 2.5 couplers. The rest of the exhaust tubing and mufflers I need to get. I am just going alumized tubing for now. I want to run 2.5 to the couplers located by the bellhousing. Then a reducer to 2 inch to the classic mufflers that I can't remember the name of right now to 2 90s that will kick out in front of the tires.
Looking at these headers the opening is 2 inch. I could open up the 2 bolt flange to fit a 2.5 tube if I welded studs on the flange. Or I could just weld the 2.5 right to the flange. Or I could go 2 to 2.5 "reducer" at the flange.

Once the couplers are unscrewed I will be able to pull the engine easily. There won't be any need to touch the doughnut gaskets unless they leak.

How are you guys running 2.5 pipe off of manifolds?

Thanks for any help.