I have an '85 RX-7 GSL with a 12a carbuerated in it. I would like to put a fuel injected engine in it. How would you inexpensively put a 13B or a 13B Turbo in it?

 

You'll need a 12A front cover and either a GSL-SE crossmember or a Racing Beat front cover mount to fit the extra length of the 13B (or slot the holes on the stock crossmember and front cover mount). You'll also need to upgrade the fuel system with EFI components. The wiring will have to be adapted (wiring diagrams for both the car and the engine can be found in the FAQs of their appropriate generation-specific sections). You'll have to figure out an intake of some sort. If you go turbo, you'll need a new exhaust system and a front-mount intercooler.

These swaps are well-documented, though. Just search in the first-gen section.