@nitro_rat and
@zoomad75 You guys have been a wealth of information and I cant thank you enough.
@zoomad75 what front springs are you running? Since your truck is so close to the same as mine Im curious about the specifics of your setup. I will likely run a very similar setup if you are happy with it, even eventually wanting to LS swap. What are you doing with that 5.3 when you go to the 8.1!?!
Looks like I could buy the cheaper Zone swaybar link and just add my own cotter pin.
I'm running 4" rough country springs up front, 4" ORD shackle flip out back. Bilstein 5100's all the way around. I wouldn't recommend the rough country springs, mainly because there are better options out there. This is the second truck I've had them on and with all the wheeling I've done with both trucks, the left front is starting to sag significantly. I've radically changed the rough country ride quality with the Bilsteins for sure, but if you can buy a better pair of springs with less stiff spring rate do it. I am running 315/85-16 tires which measure out a tick below a true 35" tire. Gearing is 4.10 with a tru-trac in the D44 up front and an open diff in the 14b full floater outback.
Like I said before the rear setup has been great for me. The stock '91 springs with the shackle flip has held up fine and flex better off road than the front does. The tonnage outback requires a little boost though. So I'll end up adding a zero-rate add a leaf on both sides out back.
When the 5.3 comes out it will go up for sale. Intake to oil pan, swap brackets, and manifolds along with the stand-alone harness and ECM. I'd probably end up selling the 700r4 with it too since I won't need it with the 5-speed going in. Before the camper became a reality the 5.3 was more than enough for the K5 with the tires and no major load on it. I could boil the rear tires with ease if I wanted to. Best mileage was up around 17mpg, but typically ran 14/15mpg most of the time. The camper changed all that. Aero drag and added weight knocked the average mileage down to 11/12 mpg and gets worse if the elevation goes up or it's fighting a headwind. I've hypermiled it keeping the speeds at or below 65mph and tucking in behind semi's to 14mpg recently, but driving like that sucks. The engine just is fighting outside of its weight class in my case. Climbing grades like Monarch Pass some 2.5 hours from my house is a battle down into 2nd gear to keep the engine wound up into its torque band. Because of the curves, you can't hit it with momentum and haul ass into it. So the curves slow you down and it's 2nd gear pushing hard to maintain 45 mph. I've driven the 40 or so miles home from work with it fighting a 20-30mph headwind and it will only maintain 65 mph in 3rd gear.
Gearing would help in this for sure. 4.56's would keep the little 5.3 wound up more in the torque curve, but I'm going to tell you now that gets old having that thing rev like that to maintain speed. LS swaps are all the rage and in the right place, they are great. In my case, I'm certain even a 6.0L would be pushing hard in my truck. This kind of combination of K5 and brick-like aero of the camper requires torque, more specifically, low-end torque. The 5.3 don't start coming on until the tach swings past 2,000 RPM and peaks around 5,000. The 8.1 starts making more torque than the 5.3 does just above idle and keeps pulling to only 4,500 RPM. My buddy Larry is the guy that really laid the groundwork for 8.1's in squarebody trucks and having been in his K10 shortbed with a fully loaded Phoenix camper, 8.1L/nv4500 drive effortlessly up mountain passes while passing slower traffic while rarely downshifting out of 5th gear it changes your outlook. Funny thing is that his truck gets the same 11/12 mpg on the highway and off-road like my 5.3 gets. His weighs in north of 8,000 pounds loaded for a week-long trip and mine comes in at 6500 now. So I've got the 8.1 sitting at Larry's place and the NV4500 at mine and just saving my pennies to get the rest of the stuff needed to make the change. Even getting the same mileage now, if I'm driving up grades or into headwinds without loosing speed I'm winning.
If your plans include big changes in elevation to get to the trails you want to travel on, I'd suggest a fuel-injected big block and OD trans (manual or auto). 8.1's are great, but becoming a little harder to source now. The next best thing is the L29 454 from 96-00 in the GMT400 trucks and Suburbans. They are really an awesome engine that has been far overshadowed by the LS swap craze. It's overlooked so much that most boneyards that sell complete engines want less for them than they do 5.3's and 6.0's. Many don't even know they are out there. I picked one up for $700 with the complete harness, ecm and they threw the 4L80e trans into the deal for free because they didn't want it. It was out of a 3/4 ton Suburban a couple of diesel bros were swapping in a Cummins into. You'd be lucky to get a 6.0 and 4L80e for twice the price from most. CaptRon's 77 K5 Camper over on CK5 is running an L29/nv4500 combo and it's just as effective climbing grades as Larry's K10 is. He bought a complete church bus with an L29 and yanked the engine and trans and chopped up the rest for less than most buy an LS engine for. Had I not had the 8.1 come into play I'd at least have the L29 going in.
I'd get yours rolling and really get a feel for how that engine works getting the combo down the road. it's not going to be fast, but it will do the task. From there you can start mapping the plan of attack for powertrain upgrades.
