Guys,
I have personally had my hands on over 20 newer Worksman frames and only one of the older ones. What I have found and seen from pictures is the biggest difference is in the shape of the down tube. The older frames had more bend radius at the two bend areas on the down tube. What I do know is that the center tube where I mount the tank is not jig located by Worksman so I do see some of my tanks fit tighter than others on the different frames. I have also found that the upper horizontal frame tube curves are sometimes more forward or back relative to the head tube and seat post tube. The one frame I used for my first tank for the INB frame was thankfully a fairly accurate one in the center tube placement. I have now seen my tanks on enough frames to tell the loose fits verses the tight fits. On the Schwinn straightbar frames every tank I have made has fit exactly the same leading me to believe there was strick quality control on center tube placement back in the day. As for Husky verses Worksman I have continued with Worksman for a couple good reasons. The Husky frame is not lugged, the Worksman is fully lugged. Lugged frames are stronger and are also how vintage motorcycle frames were made before welding was more common place, giving Worksman a better vintage look. Finally, there is nothing better, in my opinion, than a set of current Worksman wheels. Nothing special about the older or vintage Worksman wheels from what I see in pictures. The currently available Worksman wheels are the only ones I am familiar with and have used. I have a set of the Husky wheels on one of my builds and they will eventually be replaced with Worksman. Oh, I forgot to add one thing. Chris, your frame was one of the better ones by far as to gas tank fitment. It has very consistant gaps with the rear being just a slight bit looser than the front. As for your vintage frame I could shave an 1/8" off a tank to get it to fit or just replace the middle tube alltogether. That older frame is also a good candidate for a stretch and loop for your Indian BTR your thinking about.
Pat