Thanks for all the replies....final decision was made and here it is. Decided not to use the IH light switch, I already have H4 painless headlights so the headlights are already on relays, grabbed a double throw switch that I didn't have to modify the mount. Since I have USB in a rocker style switch I decided not to put the 12V/cigar type plug on the dash, I will put it in the cubby under the dash on the side. Nice to have it but don't expect it to be used much. Going back without the dash pad so that opens up other options to keep the Holley EFI monitor mount off the face of the dash. The small gauges are just sitting in tight holes, enough hole saw walk that they are not perfect but there is enough meat that I can tweak the holes to get them lined up little bit better, although not bad as is. Ignition switch bezel is a royal pain, used small files and dremel and it's about as close to perfect fitting as I could get it. Rather than sheet metal screws for the rocker switch panels I used nutserts, another thing that there is no forgiveness on alignment, but with a small round file you can open the holes a little in the direction to get them lined up and the head of the screw covers it. Used 10-24.
Next is to strip the old dash underneath and then use the 3M panel bond to permanently attach the overlay. After that shoot some epoxy primer on it and then it sits until time to paint the rest of it.
The overlay fits pretty good, I would say it's probabaly as good as you can get with the tolerances of these old trucks. however the crease above the column opening and the crease below is just a tad bigger than the dash, enough that I have a small 1/8" inch gap at the bottom of the column cover, I don't think you would ever notice after installed but I should be able to do a little body work to handle while securing with the panel bond.