Question: Bellhousing runout

[67rstbkt]

I'm trying to figure out if I need to and/or how to get a runout measurement on my setup. I am mating a Viper T56 to my Pontiac motor. I'm using Mcleod's 8710-16. The kit includes the 8710-00 bellhousing and a .700 spacer.
Because the back side (transmission facing) of the bellhousing is open, I'm not sure how I would take a measurement. Someone over on PT suggested using the front plate of the T56. Basically removing it and bolting it to the bellhousing. The problem is that the hole looks to small to fit a dial guage and get a good consistent measurement.

Any ideas? I've read differing opinions on this subject. Some say to just run it and others say it's critical to get this right.

Here's a pic of what I have:

[gearheadgarage]

Always pays to get it right