suits usually have a 6 inch drop in jacket to pant. so if you are a 42 chest, then the pant for that suit would be 36. for sizes under 40 chest though, it's a 7 inch drop. there are also some suits, that have athletic fits, meaning there's an 8 inch drop, for those tall and slender peps.
also, like simpleton is saying, many stores carry suit separates now. it's a suit, but you can purchase the jacket and pant separately, plus the pants are hemmed so that you don't have to wait for a tailor. in cali, i know that macy's carries this...try beverly center for a large selection. some of the higher end people (nordstrom, saks, bloomies) probably don't though.