Hi Jimson
Not sure about plastic tank. You can put in the YZ or IT gear set! Most of the internals are interchangable with the racer models. Clutch cover is different (Autolube) but again YZ or IT fit.
You could put some better forks and triple clamp. Loose some weight around the bike. Put some good tires on it and have fun.
They are plain reliable and with some simple bits removed, changed or added, just as much fun as that DT1!
Peter B