The smaller top 3 and bottom right are 2.10 dia. and will clear your typical 2 1/16 gage like this one..

http://autometer.com/cat_gaugedetail.aspx?gid=3199&sid=11

the smaller bottom left one is 2.45 OD - designed to take an innovate wideband O2 gage.

The big opening is for a tach like this one:

http://www.classicinstruments.com/gaugeselector.aspx?ProductCode=HR80SLF&SeriesCode=HR

It wouldn't be hard to delete a hole or blank it so the center doesn't get machined open.

Last edited by efi-diy; 01/05/2009 2:10 AM.