Would they have originally been fitted by hand? If so, there might be variations found on original bikes, particularly on Friday afternoon bikes (or did that only happen here in the UK?!    ).

Thanks for the help. I will try to find Dickie Towers on Facebook. Hopefully he has some info. If that fails, anyone want to take some measurements off a survivor. I'm thinking they should be symmetric so if you were to lay a strip of masking tape front to back on top of the tank (filler hole would be in the center) then draw a line in the tape that is the centerline of the top and becomes the reference line for measurements. Measure from centerline to tip of stripe, one from centerline to top of stripe say at the back of the filler hoke, and then one more from centerline to top of stripe at the front edge of the tank. Other measurements would be from the crimp in the tank to the stripe. One at the most forward part of the tank and then at the bottom where the stripe straightens out. Maybe one more at the end of the wide stripe at the back end of the tank. Any of that make sense? I can see it clearly in my mind!!!

73 seems like it would be one of the easier ones as the "swoop" seems to follow the lines of the tank pretty much?

 

There are several vendors that sell the decals maybe you can find some good reviews and are correct for your DT3

Gr8 is probably correct on factory fitting by hand. I know on the 70 Boss 302 the stripes where fitted slightly different depending on which plant installed them I could always tell if it was a Dearborn car 

I don't know about Yamaha, but I read an article once about a team of ladies in the Husqvarna factory that used to hand-paint the pinstripe on the 60's and '70's Husqvarna tanks.

I see Dicky Towers in the Vintage Yamaha Enduro Fans Facebook group too.

www.diablocycle.com/RT-3-360-and-DT-3-25...Gas-Tank-Decals.html

"Easier" is a relative term!  The bottom of the stripe does seem to follow the bottom of the tank but where that top pointed tip ends up could be just about anywhere.  And the front of the tank doesn't have a nice clean break line to follow either.  Dickie Towers send me a diagram for placement of the YAMAHA decal which at least helps with that part.

The doc with the placement of the YAMAHA decal only is for a 1972...  no "swoop" on that model.  Not sure it will be in same place for 1973 so keep that in mind.