This swap cost me about $900 to do. If your car needs to be painted anyway it's
a nice cosmetic update. Here is how I did the swap.

Here is what has to be swapped and why:


Front bumper Cover #34: Make sure you get it with #25 riveted to it, otherwise
you will need #25. This bracket is threaded, and is how your bumper cover bolts
to the new impact bar. You also need the 3 air dam parts. You can get those 
from Mid America or Ecklers for about $60.


Top bumper brackets to inner fender #19: These are a little different. You can
reuse yours by drilling a bolt hole in the front, or buy new ones. Mine were 
pretty beat up, so I bought new ones. When I got the new ones I found the only 
difference was the 91-96 had an additional bolt hole in the center of the two
front bolts. $60 each from dealer

Skid plates #21: You will need these for a '91, because they mount vertical 
instead of horizontal. They are about $13 each.

Front marker lights: Differ from 84-90, they mount to #19, and are molded 
different. I got mine used. The plug for the small 194 bulb is different socket
type, so you will need to change the bulb plugs.

Fog/turn lights: Needed because 84-90 style are too wide, and mounted too far 
inward and with different brackets. MAKE SURE YOU GET the brackets, or you are
in trouble. You will need the connectors for the fog light socket, and to
extend the wires for both the fog light, and the amber signal bulb.

Front crash bar #22: Different design, needed to properly mount the new fog/turn
lights + bumper cover. Make sure you get it with #9 attached, and all the screws
#6, along with all shims #7 and bolts.

Front honeycomb/foam #35: Molded properly to fit new bumper cover. Make sure 
you get it with the screws and inserts #39, #38.


This next one is optional...

Inner-fenders: Needed because the 91-96 bumper cover sits 1" lower and farther
forward, so it won't bolt on the bottom of the inner fenders.
All 3 are different the way they come together, so you can't get away with just 
buying the front part. THE BRACKETS ARE DIFFERENT TOO, so get the two metal
brackets for BOTH sides, and the hood prop, and all associated bolts.

OR

You can use a 1" Zbracket to adapt the early style inner fenders, otherwise you 
need all 3 sections + parts. your choice.

Front fenders: Needed because body molding is part of the fender and you won't
find one to bolt to your '84-90 fenders. Though, ecklers now sells wide 
aftermarket body molding so that might be an option for you too.


Side moldings for the doors, and rear quarters: May need minor modifications 
to fit, so test fit BEFORE you paint.


Rear bumper cover: Obviously you need this. The honeycomb will need some minor
trimming, but won't be a big deal. I did it with a sawzall and a big tree 
blade. Took 10 minutes and looks great. The plug for the plate light is different
than the 84-89, so make sure you use the bulb housing from your old bumper 
cover, or be prepared to change the socket. It uses the same socket as the new
91-96 front marker lamps.

Rear tail lamps: The marker lights seem to be the same as the 84-90, but you 
should get a whole complete cover if possible.If using the center brake lamp, 
you'll need to extend a wire. You CANNOT tie off the other 4 stop lamps. What 
I did was splice into the light blue wire in the harness over the ABS assembly.


Front end alignment:

#19 gets sandwiched between #25 and the cover itself, then gets slid over the 
impact bar and bolted to #9. Align the front bumper cover (using shims) TO THE
HOOD. (this can be done by leaving the impact bar nuts lose, and leaving the 
#19 brackets lose to the inner fender.

Removing the headlamps gains access to the top of the impact bar bolts, which 
allows you to add/remove shims and align/tighten with the hood closed.

The crash bar has UP & down, side to side, in and out adjustment. Have fun

Ensure hood opens and closes, on the coldest AND hottest day, with minimal gap.

I just finished mine, and this is what worked for me. Gap is perfect, no clearance
issues and it looks great. Any questions, EMAIL me.

Total cost: $900 some new, some used parts. I paid more than I should have because
I had to buy from multiple sources, than get brackets from GM. I'd think everything 
from a donor car can't be more than $600 total.