1996, what do I fix on it first? The car i own has been garage kept since 1996, and I would like to know what would be the best way to get it back on the road. What should I check on, replace, flush, etc. I do have a knock in the engine and is the inital reason why I parked it.
And would replacing the rocker arms solve the knocking or could it be something else?

11 years in the garage is a long time. Your tires are dry rotted by now. Have you started it? The engine had a knock you said. Would not be a rocker arm, more like a rod or main bearing. All the fluids need to be replaced. Tranny, oil, power steering, rear end, brakes, and radiator. The expiration date is long up on the fluids. '75 Grand Prix K57 (SJ) Coupe. That would be the 400 c.i.d. 170 bhp engine. Ran around $5400 new. Not worth a lot as a hot rod, kind of bulky and large. If it's worth it to you, pull the engine and have it rebuilt. Will run about $2500. You can get a short block but better yet, buy a Chevey 350 crate engine and install that. Tuned to 375 HP it would be a serious sleeper!

Without hearing the knock I can't tell you where it is coming from. It could be a rod knock or a broken crank which is more serious. I would find out where the knock is coming from first. Before I would drive it I would replace all the belts and hoses and the tires unless the car was setting on blocks because the tires would be flat spotted even if you kept them aired up. Be prepared for lots of things to go wrong you may find most of the seals in the car have gone bad including the brakes and power steering. After you run it a few minutes look under the car for leaks also pump the brakes a few times then pull the wheels and look at the wheel cylinders and calipers for leaks. If you don't see any leaks check again after you drive it a day or two. You may find many moving parts don't work any more and may need lubed like door locks latches and windows, speedometer cable, trunk and hood latches. Be especially careful of safety items that may fail.

Dude,you got a real classic,keep every factory,go through the motor,trany(rebuild both)go through the brake system,check the wireing(mice)Keep in mind when a car sits for that long most of the motor,trany&brake seals get dried out and crack or leak,granted it won't be cheap,but it will be worth it in the long run,things do'nt happen over nite,have fun with it and good luck P.S.I'm jealous