1978 Chevy K20 longbed with nearly 500,000 miles! LS Swap begins!

[Nick_R_23]

I didn’t like the universal set of parking brake cables with the kit, so I did some research and found a stock set that I can work with. I believe these were for an 85 K20, two RH cables.



I trimmed off approximately 1/4 of the spring to work with the travel of the caliper arms.



Cables ran!





I just need an intermediate cable and the brakes should be done. I’m measuring 102”, my two OEM options appear to be ~95 Dakota or Ram Van (102”) or ~85 Chrysler New Yorker (101.35”). Both are out of stock so I may just have one made.

[Nick_R_23]

Ended up making my own cable at 102”. Installed and adjusted the cable, the parking brake works great, along with the regular brakes! I reinstalled the brake switch and tightened down all the linkage hardware, and put the wheels back on. It’s about ready for an alignment now!

[OutlawDrifter]

Get that stuff out from under it and take it for a drive!

[Nick_R_23]

Alright, here’s the major update!

Finished under hood product!



Cleaned out in and around the truck!



Brought it outside and wiped everything down!



Loaded on the trailer to take it in for alignment!





Back home from alignment!



The truck needed a few final touches. The original starter was hanging up, and the tensioner/pulleys were squeaking, so I bought a new OEM starter and picked up a tensioner/idler/belt kit.





Back from its first official test drive!





So now that I’ve put about 500 miles on this truck, I want to give an honest review of it - and to be honest, overall, I’m not super happy with it. I think I set my expectations too high. The engine is a GREAT addition, the turn key running is amazing, it has quick, smooth power delivery, good acceleration, and is definitely what this truck needed! However, everything surrounding it is so outdated that it still feels like a chore to drive.

The biggest drawback is the SM465 - I wish I would have swapped this out with a NV4500 or the new TR4050. Hell, even a 4L80E would’ve been a good compromise, but the clunky, partial-synchro shifting and lack of OD gear just really feels disappointing when it’s behind such a great engine upgrade. 10/10 for keeping the nostalgia factor, but 2/10 for daily driving and practicality. Also, even rebuilt, the NP205 remains difficult to shift in and out of gear.

The other big drawback is really the chassis itself. I thought with all new steering and suspension, it would improve things quite a bit. It did in a way, things feel tighter, and I do like the faster ratio of the Borgeson steering box, and the brakes have never felt this good, so I feel like the quick ratio box and the rear discs are 100% worthwhile upgrades on these trucks. However, I think some issues are just by design - the truck still feels floaty at highway speeds, bumpsteer still exists, and the suspension is still jarring. The frame feels flexy while taking corners, and overall it just doesn’t feel solid or smooth to drive.

So I’m left at a crossroads - the truck is “done”, and driveable. I can keep it as is and try to enjoy it, although I’m not very excited to drive it as is. I can make some more upgrades, mainly the transmission and possibly the transfer case. I’m not sure if there’s anything I could do to improve the chassis at this point. This would solve the worst parts, but I’m still left with SFA and a flexy frame. Costs would probably be ~$7500 to upgrade just the drivetrain.

However, I may have found a completely new avenue to take with this truck. I was given a 2002 GMC 2500HD 4x4 with a Duramax and Allison. The engine needs a pump or injectors, but apparently was well maintained to that point and they decided to buy a new truck. The body is rough, and the chassis is an extended cab shortbed, so I’m not sure if that’s equal enough to a regular cab longbed, but that’s not hard to solve. I’m considering just doing a body swap onto this newer chassis, and gaining EVERYTHING modern, plus additional capacity.

What’s everyone’s thoughts?

[OutlawDrifter]

Tough to meet expectations the brain puts on a project. Been there with similar results.

If it were me, I'd swap in an overdrive. That in itself will increase the driving enjoyment. Suspension is tough, unless you go with some ORD Soft Ride springs or something like that, there isn't much you can do with these pickups. My '79 K10 had the snowplow package and rode like a lumber wagon.

Save the diesel and running gear for something else.

[Honest Bob]

Ive done nearly what you have (except I went with a 4l80e) and agree with you on the suspension, ride quality, and creature comforts.

Part of the mushy feeling is probably the big tires on little rims and there is no way I am putting anything larger than MAYBE a 17" wheel (Im guessing you are running a 17" though?) on a squarebody.

Do I want the truck to ride better? Yes, and as mentioned the offroad design custom springs are supposedly the ticket but then I'm lifting the truck and messing with the load capacity both of which I dont really want to do. Im sure a 2" lift wouldnt be horrible but I am gonna be tempted to go with larger tires which is gonna make it feel even more floaty.

The windshield wipers are another area in need of improvement but the kits to fix it are super expensive.

The 2 wheel drive squarebodies drive so much better, the 4x4 ones just are what they are.

I dont remember if you went twin stick on the np205 but that in combination with the adjustable shift detent kit improves the np205 shifting to be as good as its gonna be (less finicky). An NP208 has a lower low gear and is alot easier to get in and out of 4x4, I kinda with I went that route.

[Nick_R_23]

I think I’ve decided to move forward with this new direction, but keep the truck together in the meantime. I can’t justify the cost of further upgrades to the stock platform, the benefits just aren’t there for the expense, and by the time I spent that money, I could have a very nice GMT800 chassis under here with everything I want. An RCLB GMT800 frame is only 1.5” longer in wheelbase, and ORD zero rates or spring pin relocators will fix that. The HD frame versions have a built in lift, so really at that point, I’m just fabricating body mounts and shorting the rear driveshaft a bit.