The TC88 in my 2003 came with 2 kinds of outer cam bearings. One is a roller bearing and one is a ball bearing.
Some of the outer bearing replacement sets contain one roller and one ball bearing but some just have 2 ball bearings.
1. Are they interchangeable and does it make a difference?
2. If i go with one roller and one ball do i need to extract the roller bearing race from the cam or does the new bearing just ride on the existing race?

 

The ones with 2 ball bearings are for gear drive cam kits. Taken from the Andrews website:
Andrews Products "G" series cams which use S&S gear drives have ball bearings on both front and rear cams. Since gear drives generate much lower bearing loads than chain drives, there is no need for roller bearings. Also, gear drive cams with roller bearings will make more noise during engine operation.

To answer your second question, the race for the bearings should stay with the bearing when you press the cams out of the cam plate. If the race for the roller bearing stays on the cam you will need to remove it. New bearings will have new races with them.

Make sure you replace the inner bearings with "full complement" bearings while you're there, ie: Screamin Eagle, S&S, and probably a few others.