I prefer Full Throttle. I've heard it's beefier, but I've never seen the two side by side. I had a 12" Full Throttle brand on my 2001 Silverado . Even in it's box, the kit drew attention in the shop for how heavy and thick it was. I cleared 37", no rub with ease (FYI unless I missed it, I don't see a GM Whiplash kit marketed as 12" anywhere on their site). With optional keyweighs and re-arched springs, I was at least 14"...17 1/2" easily with the tires...and I did NOT have to resort to torsion bar cranking. I was going to put 40" on it (still no body lift), until I rolled it. Totalled the truck, but the kit was unscathed. Attached is my "after" pic-- ouch. You guys in CA and south TX have it good--lots of experienced Full Throttle installers. None near Dallas.
Due to my experience, I now think that 12" kits and anything bigger than 37" tires is downright reckless and stupid for a daily driver at anything faster than 60 mph-- I coulda been killed-- for what? Looks?? 10 grand in improvements down the crapper. Cruisin on the trail or around town--cool. But on the highway, it's plain dangerous...I don't care what anyone says!
For me? I'm definitely looking at Full Throttle, only this time, their 9 1/2" kit and 35's. No rub, no body...their kits aren't cheap, but I can certainly attest--first hand-- to their integrity.
Check it out yourself.
Full Throttle
Oh...and good luck contacting Whiplash. I sent them 2 e-mails at their website 6 weeks ago inquiring about 9-10" kits and haven't heard back from them yet. Now I'm definitely staying with Full Throttle when I buy this time...