Does any place list an assortment of 2-Way Cat replacements?

[rmay635703]

I am tempted to install a cat on a very old car that does not have one, because it can run lean (or rich) randomly I would prefer an old reliable 2 way cat.

Does anyplace have a variety of different models so I could match up my exhaust pipe size to the cat?

Thanx
Ryan

[rmay635703]

https://www.discountconverter.com/universal/index.cfm
This is the closest I can find, not quite what I was looking for but getting closer