Re: Info regarding 1990 GSX-R750
A cheap piece of crap is not worth restoring. Trust me, you will spend much more on the restoration then you will every spend on a nice, low mile 1990. Look for aluminum rust (spider webbing on frame). Pull seat off and look at battery box for rust. Fairing cracks are a problem since buying good condition fairings is next to impossible. Look in tank for rust.
You will likely need to rebuild/replace brakes, carb kit (needles/gaskets), clutch, fork seals, cables, wheel bearings, swing arm bearings, air/oil filter, spark plugs, tires, chain, sprockets, starter motor, battery.
If you really love the slingshots then it is fun spending the $3-5,000 bringing it back to nice stock condition. If you are looking for a cheap old bike, this may not be the way to go.