Were you using the Holly injectors? If so, that is your problem. The 3.4 injectors are WAAAAAY too big for the 2.8.

To answer your questions:

No, you don't need a Holly injector.
Yes, you probably can use the 2.8 injectors.

You should also be able to find new injectors at less that $100. There are several 2.8/3.1/3.4 S-10/Camaro sites that sell them. I don't know of one off the top of my head.

Good Luck,
Michael