You could look into a bolt on pressure gage.  You would have to cut and weld a plate onto your tank and install a float mechanism.. The float inside communicates with the outside indicator with a magnet and  turns a dial gage. Piggy backed is the sender to light up the led indicators.  I have one on my LeSharo camper.

  http://www.rochestergauges.com/Pages/PDFs/6200.pdf

  I work with high pressure pipeline welders. Set up and prep is 90% of the job.  Welding the required plate to a tank sitting on a work bench is quite easy for a qualified welder.

  BTW--NVC;
  The Rialta is not based on a Eurovan chassis, The chassis is a Winnebago "H-Body" with a Eurovan or Renault Trafic cab attached. This way Winnebago imports vehicle "parts" instead of a vehicle. Saves on tax, tariffs etc.

  Chris C ~ Wisconsin
  90 MV
  91 GL
  88 LS

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  David Johnson wrote:

PS - random thought - didn't late model Vanagon Westies and all
Eurovan poptops have a 3rd LED indicator for propane level?  I know
the Rialta based on a Eurovan chasis had one.  So how did that work?