The way I see it, this is more for a nice car that you want to Drive the piss out of and want to handle the best it can. I wouldnt do this to a car that has potential down the road value, but for a regular run of the mill Mach 1 it would be great. It is a very expensive way to go though. As mentioned above it will add about $20k to your build bill. That being said though, all of your major systems will be the best they can be when your done, so you should be set for years of driving. You will want to blast the underside clean, fit the chassis, make all your cuts and bolt it in place, check square. Then you can blow it apart and paint the underbody. epoxy, paint, undercoating. Just make sure if you undercoat it that you dont apply undercoating where the chassis and body meet, otherwise your attachment points will not line up.
This would be a great option if you were doing a Coyote restomod. It would be pretty sweet with a coyote and a 6 speed automatic. Or a drop out package from a GT-350 (from The Parts Farm).
An alternative to this would be to take your car to Chris Alston Fab and they will custom fab you a New front Frame system, drop in the rack and pinion steering, coil over front IFS, Full Subframe connectors with G bar and Axle Retainer, along with a 4 link and a Moser 9 Inch fuil floater just like the Schwartz guys use for under $10k. You will have basically the same thing for half the price.