As others have said, Bevels are horrendously expensive, and whatever you end up with, unless you research it and make it original, will not be worth much as a whole bike, regardless of how nice you make it if it's not original. You could easily spend 2 or even 3 times your original budget and never have a chance of getting your money back. A 750GT would be nice, and they're sought after but without the right engine it's a non starter, the 900/860 GTS things aren't very collectible and i wouldn't even bother looking at that except to part it.
What i would do is part out the two twins, there is some value in the parts, especially if you have two complete engines, and restore the scrambler properly, correctly, accurately. If there's a profit to be had from the parts after you recoup your outlay and you spend the profit on the scrambler and get it done you will have a sought after collectible for no personal outlay of cash, that's a smart and good deal.
Whether the numbers work depends on what you paid initially (which is where you make your money most times) and what you can get for the parts, I know what i would pay for that lot, and i have a fair idea of what it's worth parted out, it just depends on whether you can pace yourself with the scrambler and use your sales to fund the build as you go. Bike restorations are usually done for the love, you have to be lucky to realise a profit unless you have the right bike to start with, of those three the scrambler is it.
Be prepared for heartache though, disappointment is in your future if you take it on, vendors who promise quality work and stick to timelines rarely do, their quotes will blow out and you will be frustrated that no one sees the standard you're expecting, or if they do they will promise it but rarely deliver. This is where costs can skyrocket, paying for the same job over and burning fuel, phone calls, time, stress etc dealing with people who just don't care or finding ones who do.
I restored a Husqvarna 400 cross, it was 95% complete, but had been seriously messed with, total cost of parts and shop work was about 12k, i sold it and made a small profit but didn't factor in my time or all the incidentals. I sold it because it was too good to ride and i got an offer i couldn't refuse but i was paranoid about marking it LOL. I was satisfied with my result and i did enjoy building it but a "restoration" is only as good as the accuracy that goes into the build, the devil (and the money) is in the details!
