340 Manifold Flange Question

[DusterDaddy]

I have this set of 340 manifolds I'm going to run on my Duster Project with a mild build 318. I need to get the proper flanges for when I do the exhaust. I have seen some Chrysler aftermarket 2-1/4 flanges on Ebay and am wondering if anyone has used them or has a better solution.
Also wondering why the outlets are slightly different shapes and sizes?
I had the heat riser holes welded up at wrought iron shop....

 

[Treblig]

The passenger's side manifold only has a 1 7/8" exit hole and most muffler shops can swedge a pipe to fit the bell shaped connection. The driver's side requires a flat flanged pipe with 2 1/4" hole gasket. I also sell the flanged pipes for the 360 magnum and the 340 large hole driver's manifold. Unfortunately the 340 passenger manifold you have won't accept the 360 magnum flanged pipe I sell.

Treblig