Thanks to all who responded and for the great picture of the work site on the firewall. I will have to somehow upload some pictures as what I had to work with was significantly different. Where the picture shows a bare firewall, I had a grommet poking through that apparently allowed access for the wiring or tubing that controlled the cruise control mechanism. I did pop the grommet out to get it out of the way but a trial fit of the rod through that hole just confirmed that it was not in line to allow the rod to work correctly. The first thing for anyone considering this install is to strip the firewall by hand using a chemical or metal stripper. Do not go with power as it will erase the dimples! They are not all that visible, at least they weren't on my sheet-metal and even though I had been reliably informed they existed, it took a leap of faith to confirm that the vestige I found was indeed the actual drilling spot.
For my '85 SS firewall, the actual hole for the rod locates itself about 1-1/4 inch to the right of the opening/grommet for the cruise cabling and almost at the junction where the three planes of the firewall come together Using the dimple that I managed to finally approximate, I drilled a pilot hole 1/2" in diameter and then test fitted the rod through it to see where I was in terms of proximity to the pedal arm. Once I knew which way I had to adjust the hole, I used a step drill to open it up to 7/8ths". Using the boot internal diameter at the flange for a guide, I knew I could create a hole as large as 1-1/4", but no larger as it would end up over running the flange and being too close to the hole for the grommet. Using the 7/8th" hole I again installed the rod, attached it at the Z-bar end, and then reached into the foot-well for the pedal arm to end where the rod had located itself and where it had to move. Once I had marked the hole for clearance using a black marker, to gain the needed space I went with a drum sander accessory on a Dremel tool. After that it was tweak the hole slightly and test fit the rod, repeating as needed until the hole was just big enough that the rod came and went back and forth without touching the edges. All stop right there. Cleaned the hole up with a little coarse sandpaper to round off the edges. Slip the boot on the rod and install the assembly back into place. Check the lay of the pedal and it was good. Rotate the boot into position and make sure it didn't encroach on the existing grommet hole. Secure it with a couple of self drilling screws and call it a day. For those reading this who wonder why I didn't keep going, the answer is no permanent heat to speak of in the garage. I do have plans to take some pics of the finished install and for those who wonder why I didn't take pics as I went along, thinking about pics didn't occur, I was too busy trying to be careful and not ruin the hole by overhogging it or moving it in the wrong directions.
Thanks again. Will post as I move forward with this build. The next item on the agenda is stainless brake lines and after that it is back to doing floor pan and firewall grafting. CopperNick
