Suzuki inline 4's of that vintage were, IMHO, among the finest street bikes made.
They came in 550, 650, 750, 850, 1000, 1100 & 1150 flavors. "standard" E & T model, "cruiser" L model, sport-tourer G model, and a few S model Katana's, too. 2-valves early on, and 4-valves later in the run.
The G, and the L, too I think, were shaft drive. I had an 82 GS850L and it was a shaftie.
The big GS's are bulletproof in normal operation with the exception of their stators. They had a weird-Alice external circuit that could lead to overheating and cooking their stators. Pricey, but the problem is well-known and fixes are readily available. If you buy the bike, you can google the fix pretty easily. A pretty dedicated forum support exists, too, although I can't remember the exact site address off-hand.
If your specific example looks and sounds good, you almost can't go wrong.
Good luck with it,
Kirk