i have a 87 formula 350 thats needing a dash replaced, the dash harness was also butchered for a stereo and remote start. I found a dash from a 91 305 bird with a intact harness. Would the harness work from the 91 305 in my 87 or is it totally wrong?

 

It can be repinned to work, but is not a direct swap. Compare the pinouts for both years and move the necessary wires around on the C100 (near the booster) and C207 (near the ECM). The 87 harness uses a C221 (near ECM) which the 91 harness wont have, but is easily added

Year break downs for the dash harness:

Camaro - Firebird are not interchangable
90-92 V6/TPI are slightly different from TBI, but very easy to modify
89 is specific but can be easily modified to 90-92
88 is specific, but very similar to 86-87
86-87 EFI
85 EFI
Carb and CFI dash harnesses are hit/miss. Better to find the same type of car you're replacing or update to a newer harness