ive got a m4 head now with roller rockers, going to get a crow cam for it. was wondering if there is any improvement in high rev springs and porting the head. and has any one done this and it it a huge gain?

Youll find you wont be able to get a cam for the roller rockers.
My head was heavly ported and polished and skimmed but cant really say on the gain as i had the whole motor done at the same time with other things to up the gain
They took a reasonable amount off in the ports so its worth it with other supporting mods

Can you put 1st gen lifter gear in a newer head? I have a cam for a 2.6

i can get a reground cam for the roller rockers from rwp but ill get that when i go turbo and aftermarket computer. i should have a bit responce since iver droped the balance shafts

petew and some other put cams and sloid sigma lifters in there cars. check the early first gen threads.