im thinking about buying a 05 duramax my question is what suspension lift 6in height should i get, im pretty tough on trucks off road crawling around rocks and romping it through the whoops now i want somthing that will at least let me go decently fast not crazy i havent found somthing that sounds al that great.

:ro) CST

There is plenty of information here try a search.

Have you considered a solid axle swap? My 05 should be here in 3-4 weeks and is getting a kingpin dana 60 within a few months. offroadunlimited has a very nice kit or many local 4wd shops can fabricate the brackets, steering ect needed to do it. Yes it is a little more expensive but many ifs guys that tune there max snap swaybar links on a regular basis. My buddy with a 10" ifs kit has nothing but problems. That being said if you dont plan on tuning up your d-max an ifs kit may work for you. My 2001 had the 8.1 and a 6" superlift with no problems other than a little launch shutter. I got axle off e-bay for 1000.00 + 300.00 to ship it. Needs to be axle from a ford so the diff is on the left of truck(78-79 if you want high pinion kingpin axle) or some guys use a chev/dodge axle and change transfer case or use a clocking ring. Most who have done ifs and solid axle swap say the solid axle swap is the very best mod they have made to there truck, even over the performance mods. If you still want ifs lift the rcd and fabtech kits are very nice and are good quality.

PRO COMP here !Click on the link below in my signature to see how my rig looks like with the ProComp on.

LATER!

im thinking about buying a 05 duramax my question is what suspension lift 6in height should i get, im pretty tough on trucks off road crawling around rocks and romping it through the whoops now i want somthing that will at least let me go decently fast not crazy i havent found somthing that sounds al that great.
Skip the IFS lift if you are going to be rough on it like you said. The IFS offers no real flex and the t bar crossmember needs to be dropped as high as you lift it making it a anchor high centering you on any difficult rocks and whoops.
The down side to the older Ford HP 60 is the track width is a little narrow and it lacks the ABS sensors. You can have the sensors machined on by a shop, not many do it though and then run spacers on the hubs, then it will need a complete overhaul with gears and bearing and a locker, $2500 total maybe.
Dyna trac and a few others sell a complete bolt in axle with ABS ready, spring pads, rotors and calipers for a little over 5 grand. Plus the Offroad unlimited kit at $850, $300 for a driveshaft, shocks at $150, brake lines at $100, and $1000 for a crossover steering system.
Not cheap but in the end you will be happy with it.

I vote BDS or RCD ill be getting one or the other.

My truck's getting the RCD installed today. I just got rid of an Avalanche with the Fabtech on it, and wasn't too impressed with it. The trailing arm bushings creaked under weight shift, and the front end was a pain to align (this could have been the tech's fault). Another reason why I didn't choose the Fabtech for the 2500 was the amount that it widens the front track. I think it's an inch +/-, while the RCD only widens it 1/4 inch. The Fabtech is cheaper, but if you were to upgrade to Bilsteins (which come in the RCD kit), the difference is only $70+, depending on what you're paying. I have no experience with the Pro Comp, but more people told me to stay away from it (improper fitment, bad warranty service) than told me to get it. I had a CST 7" lift on a 2wd Silverado 4 years ago, and the truck drove like it was stock. I don't remember any issues with it at all

I Would Go With Cst There Are The Best

We lift about 10 HD's a month at the shop I work at. We only use Pro Comp and Full Traction(a local company that copied Pro-Comp). These are two of the only kits that reinforce the steering so you will not have issues with wearing out pitman and idler arms. I believe the CST and Cognito kits also offer the reinforcement and from what I have seen are excellent kits, but they are definitely priced at a premium. The market here is quite competitive, so we generally like to keep the price at around $2k installed.

Mike