73 GT250K petcock:http://www.suzukipartshouse.com/#/Suzuki/GT250_(1973)/FUEL_COCK_(GT250K/021110001/56021110034
70 T250II petcock:http://www.suzukipartshouse.com/#/Suzuki/T250II_(1972)/FUEL_TANK_-_FUEL_COCK/091290001/560912900D09
They use the same petcock: part # 44300-18450
The lever gasket, part # 44341-18450, will fit both. They just didn't show it as a separate part for the T250.
I replaced the gaskets on a GT250K & T350R. No leaks on the T350R but couldn't get the GT250K to stop leaking. Eventually gave up & replaced the GT250K petcock with a Pingel vacuum petcock for about $150 & its works great. NOS petcocks are still available for around $300.