[bobcowan]

That's a good way to start. You have to have a flat and square surface and structure to start with. Then square everything to the squared surface.

I would not recommend use the carb or intake to measure the drive line. With each connection and with each component, you have the potential for a small margin for error. Eventually, all these small errors will add up to something significant. Basic scientific principle.

Ideally, you would want to measure the drive line angle at the transmission tail shaft. But I don't know of an easy and truly accurate way to do that.

How much down angle (compared to the drive line angle) you run depends on the type of rear diff you have. I have a solid mounted IRS, so I run 0*. A stock rubber 3 link rear has enough flex that you might need as much as 4-5* of down angle. It all depends on the application; including facters like vehicle use, tires, power level, etc. If you do a google search, there's some charts and opinions available to get you in the ball park.

Pinion angle itself doesn't really cause wheel hop. But if the rear is loose enough to cause oscillation of the pinion, that will probably cause wheel hop regardless of the static pinion angle.