When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
So you want to keep the original gauge working, and add an additional gauge? Shouldn't be a problem--grab a 1/4" pipe tee and maybe some other various fittings and plumb them to the original sending unit's hole.