Just confirming it is a direct bolt in. You will need the nuts from the LS1 booster as they're smaller than the 3rdgen one.

I replaced my stock rusty booster on my 83 after my pedal went stiff. During driving around, out of no where, the pedal went hard. Driving it some more, there was a loud snap/crackle/pop. Had to drive home on it, not fun. Got my hand on on a 98 booster and gave it a shot. Bolted right up and fixed my problem. Also have a 98 master cylinder in case my stock one didn't work. Thankfully I didn't have to resort to it and no lines had to be undone.

Under hood two nuts were I think 15mm and 4 interior were 13mm on the LS1. The stock thirdgen ones were 15mm inside. You WILL need deepsockets for the ones inside. You will also need a swivel as it can get pretty awkward for the ones inside.

It is a very simple swap. I have done it in a couple of hours just now. It would have been faster if I didn't have to run out to the store for deepsockets.

Hope this helps someone in the future.