I am slowly getting some issues with my car sorted out. Right now I have a dual bank Westach cylinder head temp gauge and I have senders on cyl 1 and 3 spark plugs. I am getting really strange numbers that are obviously not accurate. I am interest in getting a new cht gauge however I would like to be able to monitor both banks with only one gauge. I am out of room for other gauges. If there is a low price option for a dual bank compensated gauge- great but I am not aware of one.

I am interested in getting a Dakota Digital gauge. Does anyone know if it is possible to put senders on both banks and have a switch in the cockpit that allows me to choose which bank the gauge is reading?

You would need a matched thermocouple switch...best to check with the gauge vendor and see what they offer

You can do all 4 if you want, but I understand #3 runs the hottest. The gauge is not bad, but the probes are not cheap.
http://www.aircraftspruce.com/catalog/inpages/1105698.php

I believe Dakota Digital uses K-type thermocouple probes. This means that you can order a rotary selector switch from Omega Engineering (or some other instrumentation company) to wire all 4 thermocouples into and have a single selectable output to run to the gauge.

Example of a rotary switch we used on some old test equipment at work:
http://www.omega.com/pptst/OSW_SW14.html