Engine swap

While it is the same basic block there are a lot of differences in the engine. The 1987 would be either a throttle body injection or a carburetor engine while the 1989 in the Firebird is multi-port fuel injected. If you had the TBI the swap is a bit easier as you can just swap the intake and a few sensors over to make the Firebird engine work. If it had the carburetor version you need to swap many more parts. There used to be a kit available that let you drop the 3.4 out of a 1993-1994 Camaro into them. I built my 85 that way years ago. You mixed parts from a few years but it made the truck so much better to run. Basically you swap the intake manifold over with the 2.8 parts onto the 3.4 and it drops right in. However it only works that easy if you already have the fuel injected 2.8. It was a real popular thing for the Camaro and Firebird folks to replace the 2.8. If you Google it there are a few articles still out there about it.

Nope, only real difference between them is the badges and some trim.

The 3.4 made a big difference over the 2.8 Just be sure it's from a Camaro or Firebird. They used the 3.4 in other vehicles but mounted sideways and the blocks are different and don't interchange.