An 81 i'm interested in has no exhaust and i was wondering if they came with cat.converters and if they were true duals,or 2 into 1 into 2..t/y

From what I know, those Z28s (my 78 Z had this setup) had a Y pipe into a single cat, split off into 2 mufflers under the rear seats and dual tailpipes

Yeah, I'm almost sure it had a y-pipe off the manifolds into a single cat. I can't recall the stock mufflers whether they were dual mufflers under the rear seats or if it was single pipe into a crossflow muffler behind the rear axle and out dual tailpipes (that's how 3rd gens had it set up).

All my second gens had at least true duals and/or headers on them by the time they made it into my hands.

The Z28s came factory with dual mufflers under the car with a single cat. I think canadian models may be different. Heres a part of the '81 Z28 sales brochure avaliable on this site

http://www.geocities.com/MotorCity/1293/1981/81zb7-1.jpg

from the '78 Z brochure:
http://www.geocities.com/iracez28/1978/78zad1.jpg