73 400 questions

Hey guys, need a bit of help here. My dart sport has a 73 400 out of a motor home in it, I am wanting to get some parts for it that I know I will need if I ever manage to get her on the road such as new belts, alternator, water pump then a tune up. Question I have is what do I buy parts for? Do I just pick a Chrysler/Dodge car from 73 that had a 400 in it, or try and figure out what kind of motor home it may have been or?

Thanks