The sbc is cheap and it is a good package. The rear oil pump\sump pan helps a lot in that area. I have heard that the basic layout was modeled after the Flat-Head Ford, in search of conquest, hotrod market sales and imaging. That worked pretty well.
Build a couple different brand motors, one of them being the sbc, and add up all those parts that are $5,10,15 and more cheaper for the sbc and you have saved a LOT of money over the next cheapest engine, the SBF. Money that stays in your pocket or money that can be spent on more goodies.
It doesn't take a genius to recognise a lower price. Any mouth breather knows that $79 is less then $89.
The 5.0 Fox Mustang changed that equation. The entire car cost less to go fast than any other package. The 5.0 Mustang is the sbc of the late 20th/early 21st century.
You can get a good running Mark VIII 4V engine and trans for well under $500 if you look, 290HP, and it will EASILY bolt in with all factory parts.
Caveat is the wiring, but if you do an LS engine swap you have similar issues anyway.
I recently saw an 80 some odd thousand mile one for $300 on Craigslist. It sold fast. One of my nephews found a running and driving Mark VIII with bad air bags for $290. He has sold and is selling the chassis and body parts, et. al., to maybe make the engine and trans free or even make a few bucks, and the motor and trans are going into an 87 TC.
Any modular motored Fox K-member makes it a bolt in. There are hundreds of thousands of those out there.
4.6 Cobra headers bolt on and they are showing up in good used condition and of course new anytime you want. At prices MUCH cheaper then Chevy into Fox swap headers. ($700+!)
A caveat on 4v Modullars of course is the cams. They are WAY more expensive then any other engine, BUT, you don't really need a cam swap with the 4V's cause they breath so well from the factory anyway.
The LS1 engine swap is not your cheapest performance swap.
There is no appreciable wear of the leather. It's in great shape, and there are no seam tears or rips in the fabrics. However the driver side bolster is sagging a little bit. Probably an easy fix.