Album link showing the process I took.
Doing it myself saved more than half the cost. Finding 2.5 inch pipe cheap is not easy.
Hampton Rubber had a 6 inch pipe nipple for $12 and the square key stock of one foot for $3.
Years ago, I had a machine shop make 2 of these from steel for $75 each.
My engines use four of these.
I started engine and heard a loud noise. Not much except rust holding this together. Whacking with hammer showed how thin the cast iron had become.
2.5 inch diameter steel pipe joined to cast iron flange.
Hub end formed from 5/16 square key stock.
Brazed with silicon bronze rod inside and outside.
Bimetal hole 3 inch cut the flange to inset the pipe to provide greater surface area for brazing.
I used Permatex gasket maker high temp rated to 700*F for the gasketing, and also skim coated inside of the exhaust surface. I found it holds up protecting the metal from rusting.
This repaired piece is thicker than OEM and with the silicon bronze brazed surface, will outlast me.
If exhaust makers bronze coated their iron, then these parts would never rust away.