I am doing an ACC carpet from Rockauto in my 85 burb right now. Spend the money on the mass backing, I went the cheaper route without mass backing and it makes the install much more difficult. To help with any of the pre-formed sections that need more forming go get some free sandbags and drop them on the carpet and let them sit overnight or longer. That helped the carpet really suck down into every nock and cranny. Ill echo everyone else on the hole punching, I used a screwdriver heated up and punched the initial hole from the bottom. From the top side I had a 1/2" dia metal tube that I would heat up and use to burn the holes that looked just like factory. Last piece of advice is to start poking the holes in the center of the cab first and bolt those items down first and then work your way out.
I got an Essex kit from Rockauto and having nothing but problems with it fitting correctly. I did not get the mass backing but put down Kilmat everywhere. I think that might be throwing off the fit just enough to make it a struggle.
The front cab section is about 3/8" short to the sides. Also, the spare tire well cutout is way off (too small) and I emailed ACC and they told me I have to deal with Rockauto. The problem there is I bought the carpet kit probably 3 years ago at this point...so probably going to end up making the cutout the right size and carterize the edges with a propane torch.
I was expecting a way better fit from the reviews I had seen. I did run across a youtube video where a guy is just moaning the entire video about what trash the ACC carpet is, etc, etc.. and I had the same experience he did