I just installed custom http://www.speedhut.com/ gauges in my e-body. GPS speedo is great, change gear ratio, tire sizes and speedo is not effected. They will work with your custom idea's /designs. Great company IMO.
I just welded up an oil pan for a guy with a 454 Chevy that when he was changing the cam dropped a lifter and never found it, replaced the lifter, fired the engine and it spit out the side of his new oil pan like a bullet and destroyed the starter. The hole looked like it was perfectly punched...
I have double adjustable QA1 on my Challenger. For the money I think they are great. I had RCD Bilsteins and when I went to a composite rear leaf spring they couldn't keep up. The QA1's work great though.
They use a bigger upper ball joint. You could use a sleeve to make it work on a smaller ball joint . The caliper mounts are different and do not interchange with the 73 or 72 and earlier.
http://pitstopusa.com/i-5066765-allstar-performance-ball-joint-adapter-bushing.html
Here are some...
I used a set on my e-body and would like another set for another project. Yep they are a one year only deal . I've heard they were also on some late 72 c-body's too