Install Lokar shifter on turbo 350

It's Friday night, and tomorrow I am going to install my new Lokar shifter in the roadster pickup. Based on the instructions that came with it, it looks like it should be a pretty straightforeward job. It would have been nice if I could have installed it before I had the body bolted in place, but I had to have the body on the frame and the seats installed so I would know where the shifter should go for good "ergonomics". I am going to set in the seat, hold the shifter where it is comfortable for my reach, and drill a small hole through the floor at the base of the shifter. That way, when I crawl underneath to assemble everything, I will have some idea where to mount the shifter on the support plate that attaches to the top of the transmission. (there are a number of different holes in this support plate, so the shifter can be positioned closer to or farther away from the seats)----I only want to cut the hole thru my floor once!!! Anybody have advise to give?

cut the hole small at first... that way, if it needs to be moved it will only get bigger to the correct size. That will allow for a small degree of placement adjustments.