Centering the bellhousing
 

I went to try and set up the scattersheild last night, and I kinda got stuck.
I got one of the dial indicator's from Summit, to center the housing, it has a magnetic base.

But, How do you know it's really centered on the end of the crank?
Would that not throw off the reading on the dial? I tried to eyeball it, but if a few hundred's of an inch is going to a problem, that I need offset dowel pin's (maybe). Would it not have to be correct on the initial setting?
Or does it matter?

Doesn't matter as long as it's centered well enough so the dial indicator doesn't run out of travel.

Like Robb said. You really don't need to have the indicator perfectly centered as long as the pin of the indicator is perpendicular to the edge of the bell housing. The indicator just rides around in a circle with the flywheel. Attach the indicator to the flywheel and set the indicator pin so that it touches the hole of the bell housing. I like to have the indicator set so that the pin is depressed about 0.030" to make sure you get a good reading all around the circumference. Rotate the crank one revolution, making note of the highest reading and the lowest reading. Zero the indicator at the lowest reading and spin it around again and make note of the highest reading again and a few in between - mark the highest, lowest and few others on the bellhousing for reference later. This will be your maximum run out. Divide by 2 and that is the size of the dowel pin you will need to order from RobbMc.

As long as the dial indicator stays put a certain distance from the centerline of the crank (ie, bolt it to one of the crank flange holes) then it will be lined up wrt the centerline of the crank.

Do not try to use the magnetic base. Modify, cut threaded rod, weld, whatever...to mount the indicator to one of the crank flange bolt holes.

Make sure the dial indicator needle is perpendicular to the inside face of the bellhousing. This may be difficult depending on the size of the indicator, and the mounting setup you come up with.

Get as close to perpendicular as you can. Mount the dial indicator as securely as you can.

The flywheel should be removed.

Good luck.