EI US-8A-4 Engine analyzer, was installed brand new into my C model in 2014 shortly before I purchased it. It's in nice condition. I recently upgraded to a JPI900
This is a basic monitor- two LCD numerical displays where you can scroll through CHTs and EGTs and program in alarm temp. It has a button to find the hottest cylinder. I found it inferior to a graphical monitor, but WAY better than nothing. It's compact, fits in a single 2" hole. It might be an excellent option for someone on a tight upgrade budget, might not be hard to replace later with a fancier EI unit.
It runs about $1100 new on Spruce, and I am asking only $350. I am including the 4 standard EGT probes, 3 bayonet type CHT probes, one piggyback ring probe for the single factory CHT probe - this one reads too cool. You may want new probes will likely need to get a harness.