need advice-88 turbo lebaron

Hi everone. I need some advice on my car. I bought an 88 Lebaron with a 2.2 turbo engine swapped in. I knew it needed a new head gasket so I replaced it and it runs but it has a knock in it around 2400-2500 rpm. A mechanic told me it is probably a piston pin 'cause it kinda backfires a bit. Anyway, If I have to tear it all apart again I'll probably have to buy a new head set or atleast a new gasket and they're not that cheap. I only paid $350 for the car but between having it towed to my house, buying a head set and a few other odds and ends, I'm probably up around $1000. Therfore, I've put too much $$$ into it to junk it and I don't want to give it away either. Also it's in really awesome shape. I thought about buying another engine but it would have to be turbo because the one in there now is super fast and I don't want to downgrade and I don't know if I can find a good turbo engine cheap. So should I tear it apart for a rebuild or should I try to find a good engine? Any ideas aprreciated.

Dump the engine you have and try to find a common block to swap in (89 + block) preferably a Turbo II.