Eyup Chris!
I changed over to a B44.1 from the durango, when I looked at the various chassis out in the marketplace I thought the car was of a high spec and the best value for money, plus I have experience with a B44 so that helped with my choice
from a 2wd perspective if I was to run that class I'd probably go with an SV2 - Different manufactorer but I wouldn't need a conversion kit. Would definately consider an X2C as well.
Think when it comes to swapover of parts to and from 4wd & 2wd yeah I can see where you're coming from, but IMO barring rear rims and a few other parts which could be inter changable % might find that I'd need a seperate parts package for both cars.
MikeP