LBARTLETT,
No I didn't. I started with the rear of the cab, there are two raised areas just under the rear seat that were molded into the carpet that fit really well. Once I got it centered I installed the rear seat belt anchors and worked my way forward. Between the two raised areas and the seat belt anchors they held the carpet in place perfectly of course with me sitting in the middle of the floor that helped too. Having an auto will make the job easier being that you don't have to deal with the stick. The holes for everything else I did by feel and peeking under the carpet. The mounts for the rear seat you can get creative with how you trim around them and do a better job than the factory just up to you on how to do it.
I thought about doing all the trimming before I put it in the truck but I was too afraid of coming up short. Takes a little work trying to get all you can shoved up as a high as possible on the firewall but it's not too hard to work with, just take your time and make sure of where you trim or cut.