L124C, what did you end up finding for oil pressure/temp? Did you look into the tachometer? I'm just beginning to think about gauges myself and hope to make up a new engine panel over winter. I'm unimpressed with my stock yanmar panel which is disintegrating in it's 15th year and populated with incandescent lamps and untrustworthy wiring. It's in the cockpit so everything will have to stand up to weather.
My first thought was to just recreate the current functionality with higher quality hardware - LED indicators for alarms, new tachometer, new engine gauge (may stick with audible alarm). Possible additions include voltage meter and nav/spreader light switches.
This catches my eye initially. But I know nothing about this company etc. Lots of research will follow.
VDO Marine Viewline Tach+ Gauge