Suzuki 2 Strokes

Hey everyone i just got my hands on a 72 gt380. Have a few questions this being my 1st suzuki triple. First of all i got the bike really cheap the former owner knew nothing about motorcycles mechanically wise. He thought there was something wrong with the bottom end there was a slight ticking noise sounds to me like a exhaust leak on the center cyl lower where it splits into 2 pipes hopefully i can check it out this weekend. It has had a top end job i can tell by the green base gaskets. Anyhow. Someone has changed out the round with flat headlamp bucket to a round one the bike has been painted factory colors really bad job seat has been recovered looks like the foam is 2 thick to be factory foam. Anyhow tanks and seats i think i have figured out they are the same for 72 380 and 550 does anyone know if 73 and later seats and tanks will fit the 72 frame.72 seats are hard to find just curious tank is not rusty on the inside but i do not know if it has bondo smeared on it to cover up imperfections or deep dents before sanding. Just trying to see what my options are before i get into it this winter. Everything works on the bike shows 14k miles Thanks

The early (J/K) seats and the later (73-77) seats are different because the latter have a seat lock and a cut out for the lock. The trim is divided to pass the cut out. I think it physically fits though, but will look wrong.
Mike

Although the tanks look the same, they are not. Due to the changes made to the carburetors in 74, the petcock was relocated further forward. The later tanks won't fit because the petcock interferes with the head overhang on the 72-73. I tried to put a 73 tank on my 75 550. I can tell you from personal experience that doesn't work either. The rear of the tank hits the top frame rail and that stops it about 1.5 inches short of going all the way down. So positively no, the tanks will not interchange. If you want to replace the tank, it will have to be a 72 or73.
On the seat, I would venture to say no as well. The frame definitely changed in 74. That change probably moved the hinge points, as well as the seat is cut out to clear the lock on the later models. If the seat pan is in good shape, I would get the one you have recovered. Another more subtle difference is the early seats had a real nice radius on the back that followed the contour of the rear fender. The later seats are somewhat squared off over the rear fender. In my opinion, the early seats were nicer.
p.s. Be very careful with the seat trim if you get the seat recovered. That trim was obsolete decades ago, Occasionally found on eBay, it's usually bent up junk.

Was afraid of that guess i will have to work with what i have. Does anyone know if they make a manual petcock to fit them?