I dunno, the RRS kit comes with everything and it's new. The Fatman kit, you still have to come up with the rack (most likely used, unless you buy new), struts, spindles and brakes (again, used UYBN), and a GM adaptable steering wheel (if you already have a Grant or LeCarerra you can just get another adaptor). You add up all new prices on the Fatman kit and I guarantee it'll come out to be more, especially if you make the components equal (PBR, KYB, Eibach
). In fact, I'd bet if you made it all equal and bought all new parts, you probably be able to get the RRS rack and pinion for the same price. The RRS has created a spindle especially for this setup, Fatman creates adaptors to use existing parts.
And if you've added parts up, there are far more than a thousand dollars worth of stuff extra, the Fatman kit, all you're paying for is their engineering. I know I could replicate the Fatman kit if I had one in hand, I couldn't do that with the RRS kit. I also think the lower control arm on the Fatman kit looks kinda tiny, with the RRS kit, you use the factory one (or you could get a Global West one).
It's all a bunch of money, too much for me right now, nut I'd sooner spend the extra G for the RRS kit and have everything then to get the Fatman kit and have to search for good parts.