Where to get pre bent exhaust pipes and any suggestions on how to swage them to fit over mufflers?

Yes.

You will need an exhaust pipe expander.

This ones available at Summit but I bet Hr. Freight has one as well.

Titan Tools 51364 Titan 3-Piece Tailpipe Expander Sets | Summit Racing
I'm curious if you've ever gotten one of those tools to work. I've never had any luck with those expander tools on exhaust tubing of decent thickness (16g maybe?).