Ideal wheelbase depends a lot on tire size at 104" my CJ was a little long with 37" tires.
I'd agree that the kit is pricy, but not much more than a standard TJ long arm setup. There's certainly cheaper ways to do it if you can build stuff yourself, especially the fuel cell.
Genright makes some good stuff, I fab most of my own toys - but I will be buying their gas tank skid plate for my YJ. Not worth the time I would have to put into it to build myself. And it's not exactly the most interesting thing to build anyway.