I've never mounted one in the a-piller, but I've done a couple in the centre vents and it reaches no problem. And you'll need to get a 3/8 bushing, that nice anodized aluminum 1/2" bushing that comes with the ultralites won't work.
DAMN I was hoping that nice blue fitting would be retained...I assumed it would work with the center vent mounting, but its a few more inches away on the pillar pod...how much slack would you say you had on your install?
ill toss my two cents into the ring....
my elec gauge came with the obligatory 6' of capillary tubing (i think that is standard). i dont think i would have made it from the stock sender location to the pillar. but i mounted mine in the middle console, so i went through the firewall near the center of the car.....
i would find where you want to go through the firewall (hopefully near the brake M/C) and plumb a 6' piece of string through, to see if it will make it. that is easier than plumbing the gauge and line to find it does not make it.
you could try searching for post of pics from Mike (Mustang5L5). i would do it for ya, but i get killed searching pic threads with dial up. he has posted pics of his gauges. if you see that he has a temp gauge on his pillar, it must make it (im pretty sure he runs mechanical gauges).
I ended up wimping out and exchanged the whole shebang for 2 1/16 gauges. They look a bit better to me, and I was able to get 12 feet of tubing on this one. I did get the oil pressure instead, since my stock gauge, while not accurate, seems to be ok for now. Thanks for the info Hiss.