Collecting information for a 1967-1972 K20 Surburban 5.9 Build

[Dieselwrencher]

All is great info here except for the part about off the shelf lift leaves not working. I can tell you I have built 3 square body chevys with rough country and skyjacker front lift springs, and have had zero issues with them. Now, each truck already was lifted previously and had used lift springs in them so they were essentially broke in already. I haven't had any break or sag severly due to a Cummins swap. Let's take my Longhorn for instance. It has 4" rough country springs that were in my brother's V30 for years with a Cummins. He parted that truck out and I purchased them and stuck them in this truck. No sag. Tony's V-rig, 89 Burb, had a 6" Skyjacker lift previously with a 350. The Cummins has been in there for 2-3 years and I haven't heard any issues other than it settled about an inch after he first started driving it with the 5.9. He hauls a 10,000lb or heavier bumper pull dump trailer with it frequently as well. Are custom springs a good idea? Sure, if they're in your budget. But I wouldn't say that off the shelf lift springs won't work.

I'll also add that a P-pump 24v is a great option. However, the worst part of that is the conversion injection lines are pricey and like to crack. I haven't heard of any one shop that bends them that haven't had them crack. So beware of that.