Brother in laws running the 366 spring and really likes it but wants to try the 4k spring now that its in a 1/2 ton chevy and only sees track duty. For those that run the higher rpm spring is #374 the correct number and how do you like it compaired to the 3200gsk set up? He already has the 60# springs in place, does anyone have any other cummins or bosh part numbers to the differant gov. spring set-ups? Thanks Ryan

 

374 is the 3800rpm spring, 354 is the 4200rpm spring. 366 will make more HP all around than both.

 

Thanks man for the info, which do you run? I suppose youve run them all, and liked the 3200 the best? Thanks again - Ryan