Hey all, glad to have found this lovely community! I recently acquired a 74 DT100, got about 3 days of light neighborhood trips out of it before it started pissing fuel all over, thought it was the petcock, but no! So many rusty pinholes! So I have been on the hunt for a new tank! Well I found something real close! 4into1.com sells some nicely priced new tanks, I found their "Classic Thumper" fit my 74 DT100 with very light modifications! and for $120 (I picked it up because they are the town over) You can't beat it! Comes with a petcock (16mm - kind of small fuel outlet, but it will work fine for me) and a locking gas cap! 

Just thought I would share this revelation.

4into1.com - I have no affiliation, just found them, took a chance, and it paid off! Bike works again and looks decent, at least until I find/restore an original tank.

-Ben the Bearded Weirdo

Thanks for sharing that!

Hey Ben. What kind of modifications did you need to do to fit the Classic Thumper tank?

I have a DT175B that will need a replacement tank one day soon. I managed to stop the leaks with a tank sealer kit but it was pretty bad, so I need to make plans for are replacement. This bike is completely modified so originality is not a concern on this one. 

So, I got to looking, and the stock DT tank mounts are cups on the frame, and rubber pucks on the tank, the new tank was set up the opposite, but the cups on the tank are smaller, and happen to be the right size that I sliced the ends with an angle grinder and bent them in to create a circular mount to accept the stock rubber pucks. I did trim a little off the inside of the pucks with a utility blade to get them to sit nice on the new tank. But it slid in, right height and the rear bolt mounted up perfect! I wasn't able to use the stock grommet on the back of the tank but it seemed decently snug with the stock bolt and washer. If the cups on the new tank are 
"U" shaped, you just clip the tops of the "U" shape and fold them in to become an "O" shape. Hope this helps!

Schu, sent you a message.