o.k., is the 3-hole flange on the back of the converter a standard size? if so, what size is it?

i'm wanting to put together (fab) a new exhaust for my car, but the old flange is rusted hard to the old converter shell, so i just want to use a new flange. but i don't know what size.

also, any suggestion on test pipes? they're all pretty much the same, right? any to avoid?

 

I had an ebay test pipe on my rex for over a year and it worked fine. didn't rust or anything. I just took it off because I had to pass emissions and I just haven't put it back on yet.

Jon