I would suggest a XCOM 760 in a 2 1/4" dead guage hole. I just installed one in my -3 as I was using a portable and the range was really weak. Yesterday, with the XCOM I talked to a guy in the pattern (1,000' AGL) 165 miles away, and I was at 2,500' AGL.
http://www.xcom760.com/
It has some really nice features. Dual watch (listen to 2 freqs at the same time) scan, memory, music input fade, a built in voice activated intercom.
Any good hand held will work okay if you don't want to spend that much right now. Just get the external antenna set up properly with an VSWR meter, and a good switchable 12V power source, but don't expect the same performance as a panel mount.
Good luck! Keep us updated.