GM TBI injectors come in different flavors.

TBI:


Late model Multec BF:


All injectors in the same family are physically interchangeable. Smaller engines need less flow so you'll need to find a similar injector from a smaller engine. Sometimes you can find a "pod" to use the smaller BF injectors (used on newer TBI's) on the older throttle bodies. Holley sells these for $71 each but they were also used on OEM Throttle Bodies in medium duty trucks.



Injector size should be selected for the expected power level, not the engine displacement. I saw a 400 cubic inch engine last weekend that was rated at 45 hp. Although the displacement matches some of the larger GM automotive engines, that engine running EFI would an injector that delivers little fuel.

The throttle body size should also be chosen based on airflow, also related to expected power output. It might turn out that you are better of selling those larger TB's for smaller two barrel units or even single bore TB's. The unit on the left in this image is from a 2.8L V6:


And this single bore unit is used on 1.8 to 2.5L GM engines:



Ultimately, the list at the bottom of this thread should help you find applications with smaller injectors.

http://www.gearhead-efi.com/Fuel-Inj...-Injector-Info