A couple of points of clarification:
Both the Encore and Contender have easily interchangable barrels/stocks/grips.
Encore parts interchange with Encore parts, Contender parts interchange with Contender parts. Encore and Contender parts do not interchange. I am sure that is what Grumulkin was saying, but it confused me at first read.
Both guns can be easily changed between rifle and pistol configurations but unless you buy a pistol frame to begin with, it's not legal to use the frame with pistol grips or barrels less than 16 inches in length.
If you want to use them as both pistol and rifle a Supreme Court decision makes it legal to switch from pistol to rifle. So far no case law supports the conversion from rifle to pistol. It is a point of contention that comes up fairly often. The way to avoid trouble is to do as Grumulkin suggests and start with a pistol. You can use any barrel length with a pistol, but no rifle can be configured with a barrel less than 16 inches and be legal, so be careful there.
Good luck, and I hope you enjoy your T/C guns as much as I do!