I was wondering if that is a good idea not because of the loudness(I want my truck as legally loud as possible),but I heard some things about losing torque and horsepower with single chambers. Any truth to that?

Guys run cutouts at the end of long tubes and race that way. So I would say no truth. I had two Flowmaster 30's on my 442 and it was loud.

I think they stopped making the 30's because I haven't seen them on the site

Yeah, they havent made 30s for several years and they didnt make them long