70 duster with Borgeson power steering

Thinking of installing a Borgeson PS unit - but I have concerns about how much I have to shorten the steering column. Can somebody give me a measurement from the firewall to the center of the PS unit ( which should be straight away from the adjusting nut on the unit ) or to the end of the splined shaft on the pump. Thanks Reindeer...
I presently have a Flaming River Manual Box - using their coupler / u joint set up. I had an issue when I installed the coupling to my steering column and ended up braking off an easy out in the roll pin hole, so I just epoxied the hole shut and that was my pin. I don't want to replace the column so my only option is to cut the column, leaving 2.5" to attach a new coupling. I was hoping to just buy a new coupling from FR but they don't offer a 11/16" U joint, they do have a 5/8" but that would mean I'd have to use an original PS unit. Steer and Gear offer a firm unit at a reasonable price, but what about clearance issues with headers - I'm using TTI, looks like there would be plenty of room.