Measured and mounted the LRUs to the 3 panel trays. Used #6 nut plates for all mountings, with compact MK1000-06 nut plates used to mount the 2 grounding blocks as these are small items and I was running out of the standard K1000-06 nut plates used for the rest of the mounts.
Enlarged the left hand firewall wiring hole to 1" in order to fit the RV-14 stainless steel firewall wiring fitting purchased from Van's. Used a step drill from inside the cabin to enlarge the hole, and then cut the burs on the forward side of the firewall with Dremel metal cutting disks and a Dremel grind stone. (The forward side was difficult to access due to its position very close to the engine mount.) Drilled the 2 rivet holes (#30) from the forward side using the angle drill.
Will need to find someone to help me rivet these fittings in-place as it will require driving from inside the cabin while bucking from the engine compartment. Will seal with Pro-Seal when riviting into place.