p/u a decent pair of heat exchangers, solid, no holes, but lots of surface rust. can anyone recommend a good rust remover? thanks

Get them bead blasted. They will of course rust again unless you get a high temperature Ceramic Coating put on them. Otherwise, get a set of stainless heat exchangers.

Cheaper do-it-yourself method is wire wheel away the rust you can get to, then slather on Naval Jelly (follow directions on bottle). High Temp Exhaust paint afterward but you'll have to repaint it regularly.

Sorry, but don't waste your time. Wait for a set of stainless ones.
You will spend more time than it is worth, and wait until you try to seat a set of old exchangers to your heads. Very high probability of breaking an exhaust stud.

thanks guys, would buy a stainless set but am changing engines in a few months and don't know if i'm getting a 2.0 or a 1.8 rebuild. just looking for a little heat now that the cool weather is here.

Then don't do anything - until you decide on the motor. If it's only surface rust they'll work just fine.