The heads perform differently, what setup works for the GTS would not necessarily work for the GT, TSR, etc. They all have different performance characteristics.

If your Edwin Watts, PGS Superstore, Golf Galaxy would let you, you could potentially get fit with a used driver head to the new stock shafts, You wouldn't really be able to purchase the said shaft from them though. And they're not necessarily going to let you. You'd have to find the right person. Or a small business fitter that still has stock of old club heads.

Tighten that budget. Stop going out to dinner for 2 months. Meal prep. Cook at home. Don't indulge in adult berages and you'll have the money you need in a little time. The GTS will still be there waiting for you...for 2 years. haha.

Have you tried PGA Golf Superstore of Golf Galaxy? They have used clubs that you can be fit for using Trackman. To try a GTS then compare it to a Driver that's 1 or 2 generations previous doesn't seem to make sense. You're comparing apples to oranges.

I will say that I have had fittings on every release since the TS came out and each fitting has had different results. I have bounced between “2” and “3” model heads and sometimes different lofts and shafts. Getting specs for a GTS and then purchasing a GT with similar specs might work but might not turn out to be ideal for you. I was just fit for a GTS3 8 degree with Tensei red shaft. This replaces my GT2 9 degree with MMT shaft. I guarantee that a GT3 8 degree head in Tensei red would not work for me as well as my GT2 9 degree MMT or the new GTS3 will.

While the hosel adapters for drivers are compatible back to the 910 line, the head specs and comparable shafts are not a 1:1 equivalent. Many GTS users have flipped from -2 to -3 and vice-versa from prior models to the GTS line.

Besides my local Nevada Bob’s that will offer store credit on new or used drivers with a 30 day guarantee., Golbal Golf will do that with new equipment for sure and I think 2nd Swing will do new and used.

2nd Swing will do a consultation to recommend what could work for you. May cost more than eBay but the products are legitimate and the guarantee extends past your front door.