Hi Jerry, great to hear you keeping the bike :clap:, I promise you, you will fall in love with it, the GS series was arguably among the finest UJM's built.
Not so good that the PO left you a bunch of surprises,

but not all doom and gloom, again, all od them should be a minor inconvienience for a man of your skills.
Lets have a quick look see;
The previous owner put heavy gear oil in the engine to make it quit leaking enough to sell it that cant of been good on the inards
The fact that it is still running and not making strange noises tells me you probably don't have any major damage inside.
The GS series motors were one of the most grossly over engineered, bullet proof lumps of aluminuim to be shoved between two wheels, you couldn't break them if you tried.
They, except for a very few (only the 750 four valve, I think) have roller bearing crank shafts and a low pressure oiling system, so they rely on splash, more than pressure to keep the internals lubed.
Flush and replace, you should be fine.
the studs on the oil filter housing are all stripped the guy loctited the nuts on
Quite common on these motors, remove, check the threads in the case, replace, they are just a couple of bucks at Suzuki, secure with ggod strong locktite, tap to the next biggest size if you have to and replace with next biggest studs and nuts, lots of folks here, been there, done that
Both upper motor mount bolts are completely stripped out

So bad you cant get them out I am guessing because the threads are knurled with magnesium
Both lower motor mount bolts to the engine missing and assumed the threads are stripped out
It has been years since I have owned a GSX (as all 4 valves were designated here, on this side of the pond)
But as I recall, none of the engine mounting bolts actually fasten into the actuall engine cases, they are all through bolts with a nut on the other side, if it is like the 2 valve GS' the front lower short bolts, thread into a teardrop shaped thingymabob that fits between the external ribs of the engine case, underneath.
So your cases should be fine.
the oil drain plugged is stripped out and was siliconed in
Again, plenty folk here have had to deal with that problem, a helicoil or insert should sort it out.
Alternativly, you get an oversize, generic plug from your local auto spares shop that cuts its own threads, fr that very job.
I am sure those that have been through it will chip in here with good advice for you.
1. I will replace the two bottom motor mount bolts and loctite them in since I am sure threads are gone but a bolt loctited in is better than no bolt but I wonder if it is safe to ride with all 4 bolts stripped out, Its probably been going a long time that way and the pressure is side to side on the bolts so am I right in assuming it will probably be ok to ride?
I have ridden my 1000G with the engine held in by not much more than will power,

, I think at one stage I had 2 bolts holding it in.
But, yeah, it ain't too clever, so I would not suggest it, but see my remark above.
2. The engine says it holds 3500ml of oil that is almost 4 quarts right? wow never expected it to hold that much.
Yep, correct, engine and tranny share the same oil.
Seems, worst case senario, it is going to cost you a few extra $ for nuts and studs and fresh oil and filter.................could have been a lot worse.
Keep us updated, we are here to help wherever we can.
Edit: I see Basscliff beat me to it.......he is scary.
