Flaming river makes a sliding adapter for columns.
I like the car but I am confused why you are hung up on the Fox body rear suspension. It sucked in the Mustang and packaging in your car is going to be harder than you think. Especially for how close the rear end is to the body. A few years ago I hit a huge pothole on the highway and the rear end bit the body in my Total car so I happen to have a picture of how much room there is from the rear end to the seat back. There is very little room back there for Mustang upper links as they sit so high. There is some lower versions of 4 bars and 4 links but not using stock components. You could raise the seat for more clearance but my car sits pretty high now and that is not one of your requirements for the build.
Just my thoughts. I know sometimes I think stuff up and make some drawings thinking there is lots of room only to find out when I look at the car I didn't realize things were so tight. Good luck with the build.
I've seen those Flaming River kits, but unfortunately they are WAY over priced...close to $400. I think I'll be ok with just the quick release wheel and careful positioning of the column. If not, I already have an idea for using a modified version of a column swing design used on sand buggies.
One of the reasons I went with a Fox T-Bird rear end is the tire clearance issue with the body mounted as far back as I want...it's 61"+ wide. The reasons for keeping the Fox rear suspension configuration are cost, simplicity and handling. I'll be using all the original axle bracketry...eliminating the cost of bracketry and welding. I know the original Fox suspension has a bad rep...but that is mainly due to the the factory seriously compromising the suspension design with cheap control arms and bushings. I already have a set of Granitelli racing adjustable control arms, and I plan on using Johnny Joints to give better articulation and eliminate the bushing issues. Adding to all of that, I have a set of designed for handling mono-tube gas shocks. Even using the factory control arms,bushings and shocks, for a cruiser, the stock Fox setup should be an improvement over a 2 link radius rod set up.
As far as the attachment points go, the upper has turned out to be the easiest...a pocket at the base of the frame kick up. The problem with the lowers is that the attachment points fall below and several inches out from the side of the frame. I have an idea that would work, but I'm not liking the aesthetics...I'll keep working on that. Right now I have the complete axle with control arms set up on stands to get exact dimensions and and visualizing. No doubt there will be future issues before all is said and done, but I see no reason they should be any more difficult to resolve than with any other triangulated 4 link set up...knock on wood.