Progress report:
I trial fit my seats after re-aligning the steering column. As Joel noted, the stock seat brackets force the seat a little too far over from the C/L of the vehicle. I stole his concepts and designed my own brackets dedicated for the angle I am fitting my seats at and with a similar offset to his. In addition to wanting the offset I could not angle the seats far enough back to fit me using the stock brackets so custom brackets were required either way.
I had one of our sheetmetal suppliers at work laser cut and bend them for me out of 12 gauge sheet steel. The steel is only slightly heavier than the stock aluminum brackets but with the offset bends I felt better using a stronger material than aluminum.
With the seat closer to the C/L of the vehicle I should be able to fit inside while wearing a helmet for track days. I'll test that here shortly the next time I have the spider on the car.
Next up was modifying and fitting the AC system under the dash taking ques from everyone who has gone before me with a couple of twists. I shortened the "box" that is bolted to the outlet of the Vintage Air unit as much as possible turning it into basically a cap. The coil on my unit sits far enough back into the main air box that I had room to cut the outlet holes into the main box instead of the cap that is screwed on to it. This placed the installation depth closer to the dash, further away from the firewall giving me more room to run the AC and heater hoses without having to swap the heater hoses to the opposite side of the unit.
Scribed line showing how much I cut off, this mod gained me about 1 1/8":
After cutting down and installing some seam sealer tape to seal the top to the bottom of the tub (never took a pic before installing the seam sealer tape, sorry):
Re-bent the heater tubes and re-clocked the AC connection:
Not sure if anyone has installed there unit with a bracket on the back side, this worked out well for me. The vintage air unit had nutserts to install the bracket here so I took advantage. Marking and drilling the hole in the tub was a major PITA but it is solidly mounted with brackets at two opposing corners: