I'm kind of a gauge nut, and think that it's hard to have too many gauges. I'm currently lining up a bunch of gauges to add to my K5. Some are needed, and some are just info overload, to be honest. In any case, you've got to spend it somewhere. One of the hardest ones to track down all the components for, namely the sending unit, was the trans oil pressure gauge. I figured a low pressure reading would let me know if the clutches were in jeopardy from a failing pump. The gauge was easy enough to find, a VDO 350-110 Vision Series 2-1/16" job, 0-400psi (300 would do it, but the 0-400 will cover the range), black face, white lettering, very basic. Summit has it for $26 + shipping. The difficult thing was tracking down the sending unit! It seems that a 10-180 ohm, 0-400 psi sender isn't stocked at many retail auto parts stores ("You want a trans pressure gauge in your truck??? That's different. "). Boat dealers, however, are different. If the pump starts to crap out in your vehicle and your clutches begin to slip and grind themselves up slowly, you can park and walk, but if the same thing happens in your boat 20 miles offshore, it'd be hard to get out and walk to shore (for me anyway, walking on water was never a talent of mine), so it'd be on the radio and wait for the CG. Far better to see the pressure dropping and immediately make course to shore and hope you get there before the clutches grind up all the way, or stop and see if you can do a field fix. Anyhow, the sending unit is the VDO 360-406, which Summit doesn't even list as a catalog item at this time (the gauge itself won't even be stocked till 3-24-2006), but any local large boat dealer is likely to have one in stock or be able to get one ASAP. It has a floating ground, being first and foremost a marine application piece of gear, but it does have a ground terminal for ground wire hookup. For a while there, I thought I was going to have to go to an industrial supplier.