How will it perform?

Camshaft manufacturer? Cam card?

It might like more spacer, hard to call. So you have more to test with?
Header size is good IMO. Did you maintain the exhaust pipe at 3.5?

Have you run the car with this set up since the change?
Comp cams.

1” spacer is what Dom recommended. If it wants more, I have a 2” spacer I can throw on

Yes, 3.5” collector, open headers

New build, never run.