OK...probably can't afford to go with stainless 2ltr heat exchangers so here are my choices for the 2ltr I'm installing. Exhaust Choices:

1) Use the complete 1.8 exhaust off my car now from tip to tip. I have everything including heat exchangers, heat flappers etc, monza exhaust and 1.8 hanger.

2) Use one of the stock 75 2ltr heat exchangers that I have. I have everything that goes with it as well tip to tip.

3) Purchase a set of used stock73 2ltr heat exchangers. I have a 2ltr hanger. Can I use any of the heater flappers that I have with these? Either buy a new muffler or have new ends welded on my monza exhaust.

Considerations: The pipes are smaller on the 1.8 exhaust, but they have a nice flow from the heads, unlike the stock 75 heat exchangers which have a sharp bend...but larger pipes????

purchase some cheap 2.o exchangers, or use your 1.8 he's.

the 75 exhaust is freakin heavy, and the flow sucks big time.

used 2.0 exchangers are not that pricey
you'll need a a different muffler for each of the different types of exchangers
the flappers are the same for all 3