I'm in the process of installing one of these in my 66, you're right the instructions are not very good. I used the wiring diagram to figure out which color wire in my harness did what and then made a color to color chart so everything matched up. I also purchased the turn signal dimmer switch option for mine. What a pain this POS is, two of the smallest gauge wires I've ever seen that have to be threaded inside the column to exit where the other wires do. I spent the better part of an afternoon with some baling wire used like a fish the thread the wires. I have not yet decided if I'm going to keep the original 4 way flasher switch or use the F/R one in the column.
For the terminals you will need a different type of crimper, one these is what I have,
http://www.weatherpack.com/weatherpacktools.html I already had this tool since I used some of the GM weather pack terminals for my EFI conversion.
I also had a lot of fun trying to figure out if I could use my Moto Lita wheel, in the end I had to modify the adapter and creat my own wiring for the horn switch. Having been one of the first to purchase the F/River rack and pinion kit, I should have known better than to think that this would be as easy as they say in their ads.
Remember that the left and right turn signal connection from the car will have two wires, one for the lights and the other for the indicators on the dash. I cut out a section of the insulation one one and soldered the other wire in place. I did this an inch or so above the GM adapter and used heat shrink tubing to seal it up. I purchased some extra of these terminals from a parts store in case I had problems and so I could connect the headlight dimmer switch thru the same connector.
These connectors are called GM Pack-Con and are available from Help!, the part numbers are (female) 85327 (male) 85326, there are 5 to a package.