600lb springs, comp lifters should be ok. Crane lifters are no longer around, so Crower lifters are the best lifters under $1000.

I have not had any problems using Milodon bronze gears. I drive 7000+ miles a year and haven't had one go bad, yet

As for a cam button, I have only used gear drives with roller cams on Mopars, but make sure you get a strong cover like Indy, AndyF, etc to handle the button.

I don't know about the springs. someone else will have to help you with that.