Is it possible, yes.
Is it easy to do with accurate readings, no.
There have been other discussions about using different manufacturers components together, and there is a good description of how EGT works here on the site that I believe Hoot wrote.
You'd have to make sure that both the sending and receiving components will work together, then provide some sort of switch from one to the other. EGT produces a VERY minute amount of power which is read by the gauge as voltage produced and marked on the guage as degrees.
Some systems use amplifiers, some use switches, switched lead per cylinder EGT systems for piston aircraft are common, but you don't even want to go where they cost.
So lots of variables at work here, could you just hook it up and get a reading? Probably, would it be accurate? Probably not.
I like Mac's idea of two different locations. Simple and more information.
edit info:
Here's a link to the article on how EGT works:
http://www.dieselplace.com/forum/forum_posts.asp?TID=1065&PN=1Edited by: Zeeb