is it a major job to change them in an 89 rs/305?

 

Depends upon your defination of "major". And whether you're talking about front or rear (transmission).

For the front:
Do you have to take off a lot of parts to take off to do the job? No.

Does it take a lot of time, effort? Yes.

The hardest part is getting to the nuts inside the crossmember. The "easiest" way to get to them is to drop the a-arms. Again, depending upon your defination, that's either "major" or "no biggie".

But, you could combine a couple of jobs you'd been putting off, like poly bushing or springs while you're doing the engine mounts.

The back's a piece of cake. Just need to get the car up in the air (which you have to do for the front, too), and be able to jack up the transmission an inch or so. Three fasteners off & on, you're done.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/LB9 block, ZZ3 cam and intake, WP 305 heads ported & polished, Hooker headers & y-pipe, 3" Catco cat).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, 3.08 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.