Joe Bob, Wow! $850 for the windshield sounds like a hobby killer. It cost more to ship than the stated seller above sells it for ($133 – seems a very decent price). Also part of your installation is likely the cost of the rubber gasket ($80-$100). In the stated case I believe the 79-80 Pinto's have a glue in windshield??? Probably $20 for the sealant will do. Pick it up (free) and DYI the install (glue-in is a lot easier) and it is probably done for $160.
I was in a similar dilemma as Joe Bob with my '64 Studebaker. $375 for the glass, $165 to ship, $80 for the gasket. In the end I bought a used, scratched (even bull's-eyed) windshield for $100 and $40 for a "close out" gasket. This had me wise to the current and future windshield issues likely coming our hobbies way. I bought an additional (scratched and chipped) Studebaker windshield for an additional $100, and a few years back at Pick A Part I got a Pinto windshield at their 50% off sale for (this is painful for me to tell you Joe Bob) $20.
Steel can be pounded to make a facsimile of a car body. Fiberglass can also mimic a part. Drivetrains can be update to modern. But if you have cracked glass you can be left in a very difficult and expensive situation. I just checked and this same company has a windshield for my Datsun 510 ($175) and shockingly my lowly 1973 Plymouth Valiant is an outragous $375!
Lastly I've heard of people cutting a modern windshield to fit an old car. They did it on the Wheeler Dealer Saab 96 episode where they cut down a modern Chevy Impala windshield.