Yes..It looks like a 18979 or maybe a 1981 TF2 depending if you have a rubber block like the RS.GS under the tank?
anyway, it should be embossed on the left steering stem, even under few horrible paints layers
The difference is:
The frame rear loop is nearer the seat as its takes a MC mudguard.
the steering with the right tank is still LESS than the GS version
the engine ports, disk valve and gearing are slightly different been a motocross (saying that I run one similar engine on a bike I use, with a 15t at the front sprocket and 44t at the rear is fine, just a bit more picky)
your seat base will be different to fit the mudguard, so if you do not have it, do not think to get a RS.GS one, it will not fit.
or alternatively, you will have to cut the rear loop, weld one from a TF1 or RS.GS and then you can transform the bike as an enduro.
the front forks tubes should be longueur than GS, that is very good anyway!
Mind when you order your front brake cable, it's just a bit longueur than GS.
If you need help or parts, let me know, but first you need to take a bite of paint removal (do not scratch) and check what is stamped on your frame/steering stem.
Good luck, seems like a great project...but be ready with lots of $ to spend :clin:
Cheers, Philippe
www.oldknobblies.com