Wheel base differences

I've been looking around for this information, but figured best to go straight to the experts. I have a 65 Dodge Dart GT in need of floor pans, and a front frame rail. I also recently acquired a 66 Valiant 2 door post parts car with immaculate frame and floor. Too bad much else was already acquired from this rust free car, but that is another story. My question is, between say, the Darts and Valiants, where in the build does one find the difference in wheelbase? In the floor? Shackles maybe? I ask because I am thinking of using the floors and front frame section from the Valiant in my Dart if they will match up. Again, the only issue I foresee would be the wheel base difference between the 2 cars, but hoping I can make it work. Any thoughts gang?