Larry,
I would pretty much echo what Chris said. Leave the front flap long and let it run under the windshield frame gasket. Pretty much all the foam will neet to be removed from behind where the dash insert on the passenger side goes, and the instrument cluster on the driver's side. Also, there will be a fit problem at the top of the kick panel on the driver's side. The recess that the kick panel is supposed to fit into will be too high. You can get it down a little by removing some foam up high, but the fit still won't be perfect, bit it is fairly hidden from sight. Al's panels have fit poorly at this location for years.
Get a good heat gun, as a hair dryer will not get the vinyl warm enough to really stretch it. When I get the fit where I want it, I will glue the pad and leave the front edge for last. When the pad is completely installed, I glue the windshield channel with contact cement and then I heat the flap at the front of the until I can stretch it down into the channell tightly and clamp it in place by using the windshield mounting holes to put bolts through. The flap has to get pretty warm to fully stretch the fit down into the groove, but it will make a beautiful job when done.
Another little special tool that you can make to install the dash insert will make life a whole lot easier. When you go to install the insert, you will find the the studs come nowhere close to extending through the fiberglass enough to get the nuts started. Take a couple of all-thread coupling nuts (the nuts that are made to connect 2 pieces of all-thread together and are real long), and turn down the outside of half of the nut on until it will go through the fiberglass. You will end up with a nut that has a threaded sleeve that will reach down and engage the studs and pull the insert into place, so you can put the correct nuts on. I just chuck a nut up in my cordless drill, and run it against the belt sander in the shop until the bottom half is turned down sufficiently to pass through the hole in the fiberglass. With 2 of these nuts, you only need to get the dash insert to within 1/4" of the back of the fiberglass structure to get the nuts started.
Regards, John McGraw