I am considering this mostly because I already have it.

I am thinking that I can put these into my milling machine and use an inside out boring bar to clean up the outlets and ensure they are round.

Then get a piece of thick wall DOM that I can bore the ends to match the OD of the cleaned up outlets - and match inner diameter of the outlets and then machine a flange mount and weld it together.

Not sure if I will have problems with the casting / steel interface with temperature swings.

Any concerns?