1972 dodge dart slant 6 v-8 swap

I have a 1972 dart that had a slant six, I was given the car by my sister after she didn’t change the oil and the engine blew up. The slant 6 was takin out later, along with the tranny and the driveshaft. I have a 360 small block that I want to put in it, I think that dart has the small 7 1/4 rear end in it so im looking for a 8 1/4 or a 8 3/4. I’m trying to get together everything I need. The 360 has aftermarket heads I think some people call them x-heads but im not surewhat there called, all i know is the thing used to run great, here is a video when the engine used to be in this truck:

1973 Dodge Dart

http://www.ksl.com/auto/listing/5754004

I’m thinking about getting this 73 dart with a 318, it should have the bigger rear end that I need. I know that the 72 and 73 have the same track and wheelbase length.... I also need and a v-8 k member as well as the drive shaft. I’m hoping it that the 73 has a 727 in it the owner is unsure what it has and doesn't seem to know that much about the car. Any suggestions or what else do I need that this 73 wouldn’t have ?