can i redo the exhaust before i do the swap?

i found a 1991 civic hatch in near perfect condition except for its not running atm. 200$. my question is can i put on a new exhaust like magnaflow or w/e before i do the swap? after the swap will the exhaust have to be changed too? its got the sohc in it and i want to put a dohc like a zc or a b series.
im just curious about the exhaust. i would like to put like a exhaust and cai before i get the new motor. i got this car to built and race a while down the road. dont want to mess up my da.

what kind of mods can i do before the swap is what im askin…

wow i just noticed my grammar is horrible. lol and i dont get the mesage across so clear…my bad ppl.

well the exhaust wont be the problem, it’ll either be the cat not fitting the header. Theres a chance that it could fit, but i doubt it. I’d wait