Yes, get the 4kgsk.
If you want, leave out the smallest spring from the kit to make it a 3kgsk, so that way you have the spring needed to make it a 4kgsk later.
Since yours' trans is manual, so the stronger valve springs will be good idea to prevent valve floating when overrevved or if running an exhaust brake.
On the auto, the trans (when the shifter is in "D", that is) will always shift before ~3000 rpm so the valve springs are not a huge concern for auto guys (like me).
On my truck, I need bigger turbo even with the original stock 180hp injectors. I did the AFC spring kit from TST, along with rack travel mod, 16* timing advance, 2095 Mack plug, and of course no fuel plate, the truck will hit ~48-50 psi of boost easily and unregisterable high egt to boot. Currently running a custom grinded stock fuel plate close to #100 profile to keep thee egt and boost in check (~1400*F, ~35psi max).
I want more power but I want to do some more magic to my auto trans first. I really think there's some performance can be made with better converter and some other stuff.
At bare minimum I want the trans to have billet 300m input shaft and triple disk converter installed then I'll like to put a s475 under the hx35 or so. My goal is to have a cool running 500-600 hp or so. Yeah... Down the road...
