New Insturment Cluster

[SpaceForRent]

Hey so I recently picked up a '72 GMC, as seen in my avatar.
I"m looking to replace the gauges, I like the look of auto-meter old tyme white gauges.
What size gauges are currently in it?

Has anyone done this before and any advice?

Will I be able to use the stock gauge panel or will it be easier to get a new one or cut my own (I work in a welding shop)

I want to put a spedo and tach in the two large holes, fill the 4 small ones with the other gauges and put a clock in the center.

Anybody have pics of somebody who has done this before?

Thanks!