1972 C-10 Longbed, 2 wheel drive, questions

[REEDS 72]

Okay guys, I have three questions.

What do I do about a bouncing tach needle? From idle to 2000 rpms needle bounces. Seems to smooth out after 2000. I have checked ground wire, power wire and signal wire. All seem to be fine. Does anyone have any suggestions?

I am running an HEI. I am using the power wire from the old coil. I think I have read that it is wrong to use this power lead for the HEI. If so, what do I need to do to get power to the HEI? Could this have any effect on the tach problem above?

How far does the screw in the center of the brake booster, that pushes the piston in the master cylinder, need to be screwed out?

Thanks for any information you can give me.