I have them in my truck ,I installed them when I changed the cam when the conversion was done back in late 2000.
The springs I didn't change them they say you need to but for the few times I have it close to that high of rpm I run out of gear and boost for my turbo WH1C (37 psi ).
I don't plan on changing them unless I do more upgrades to the engine.The engine runs just like it does @ 2000 rpm I can't tell the difference.If I was to run at the higher end of the rpm than I would change them .
Ask tndonor he loves the truck and the power it has and always ask now what be done your engine everytime he rides in it.
Scott