[71pp'sGP]

Ok guys, just had my engine rebuilt on my 71 Grand Prix the car is a beast......one problem the guy who built the engine at enginelaboftampa.com told me my temp sending unit wasn't working properly so I'm needing to change it out......its the 3 prong unit, I've looked from one end of this country to the other and can't find a 3 prong sending switch anywhere. I've found 2 prong temp sending units will they work?......is there any other alternative I was told to put me a after market temp gauge. But I really want to keep the car as original as possible.....