OK, quick recap since I'm pretty new here. My son turns 16 on friday. I bought him a pretty raggedy 84 TA, with the intention of spending the time between now and when he gets his license getting her back to beautiful.
I found - and replaced - the fenders, hood, and bumper, and that's pretty much it for the exterior until we get it painted. I wanted the body damage fixed before I present it to him, just because first impressions are important, and I didn't want him to think it was a crap car from the "get-go".
Now comes the interior, and my lack of knowledge here is quite high.
I know that many parts , Both in and out, are interchangeable through the whole span of third gen, but I'm not sure which interior parts.
Today I found an 87 (body only, no eng or tran) for sale nearby, and I am considering buying it as a "donor car" for most of the interior. (the inside of the 84 looks like a grenade went off in it, and I need to replace virtually everything) But before I commit, I would like a general consensus if it is in fact a good idea. Like percentage wise, how much of the interior is interchangeable between an 84 and an 87?
When I bought the front end parts, I found out that although the hood and fenders of an 89 are the same, the headlights are not, they have different wiring. So now I have an extra set of headlight assemblies. I am wondering if the ratio is approximate, and if the usable parts will justify the expense. I figure the parts I need are worth at least a few hundred bucks, and I can probably part out the rest and get a lot of my money back. But if it turns out I can only use the seats... I'd be better off just waiting until an 84 (or another, MORE compatible year) turns up.
Thanks in advance for any help You can give!

 

Everything from your 87 will swap over. However, the Firebird interior changed in 85. The console, gauge cluster, dash are the biggest differences. The seats will bolt right in. The carpet is the same except for the heel pad, which is not a big deal. All of the interior plastics should be the same.

I prefer the look of the 82-84 firebird interior over the 85-92. Maybe b/c i have have 2 84 cars. It is much harder to find parts for the 82-84 cars. So if the 87 is in good shape and and you want to clean up the car everything will change over with a little bit of work. I believe the gauge cluster will be the only thing that will not work with out some modification. Cable driven vs. Electronic driven spedo. New carpet and 4th gen seats which can be had at fairly reasonable price go along way in these cars.