Honestly, sell the car as is, get what you can. I picked up my 94 Fleetwood LT1 with RPO V4P (tow package) for $3800. I have seen them as low as $2500, and a Roadmaster recently for $1250.
Look, I'm not arguing that it's more money than the car's worth. On the other hand, every example you've sited has a USED engine with some number of miles on it that may or may not need work in the near future. You can't exactly compare that to a brand new engine. Is the used car a better value? Sure, almost always.
I do my own work (obvious reasons why!), and I still can't bite anyone charging that much just to R&R an engine.
So you think you can completely R&R that particular engine, with all the accessories, emissions equipment, likely rusted fasteners, etc, in less than 20 hours? Including tuning the new engine, break in, etc? With enough confidence in the work that you'll also provide the customer with a warrantee? All I know is that having worked on my own 86 307, I wouldn't sign up to that. It took me a couple of evenings just to pull and replace the exhaust, since I had to torch off a couple of the manifold bolts, pull the pass side manifold (which means pulling the oil filter adapter), heat and remove the two broken bolts, install helicoils, reinstall the manifold, repair the busted EFE on the other side, and finally put it all back together, install the new O2 sensor through the gap between the inner fender and frame, fire it up, then pull it apart again because the parts house gave me the wrong exhaust gaskets and they didn't seal properly (307s have smaller exhaust ports than any other Olds V8).
It isn't like it is a FWD car that is a pain. $1750 is steep for a rebuilt 307. That better be a high end rebuild, ported heads and all. Nothing less for that price.
Apparently you haven't priced stock rebuilt long blocks lately - or custom built engines (try $7k - $10K). Keep in mind that the much higher volume of SBCs keeps their price lower. Also, as I noted I only checked one source (ATK Engines) that I've had good luck with in the past, though mainly on modern 4 cyl motors. I'd certainly do my own rebuild on an Olds V8. Of course, I also have all the tools, hoist, manuals, experience, etc. to do the work. There's a cost associated with all that as well.
It will always be an older car. If it means that much to you, and you have that sorta $$ to spend, fine, no problems. But honestly it is quite inflated prices. Shop around, dig up other alternatives. Find out what the engine swapping laws are in Cali. You might be much better off getting a more modern engine (LS1 with 4L65E, you can get for $1500 for the PAIR!) and drop it in. THEN and only then it is worth $1500 to pay someone to install for you.
And those prices are for freshly rebuilt engine and trans? Of course not. And naturally, $1500 doesn't cover the cost of the computer, wiring harness, electric fuel pump, different exhaust system, different hoses, different throttle linkage, different motor mounts, different driveshaft, different trans crossmember, etc, etc. Yeah, that's MUCH less expensive.