LA 360 engine

Will this 360 bolt up in my 64 dart with out a lot of changing have a 273 in it know factory 4- speed

You would need to get a flywheel for an LA 360, and a bigger bellhousing. You would also have to get a Z bar from Brewers that mates the factory clutch linkage in your car to the later/bigger bellhousing. Those are the "needs", and there would probably be wants as well....like headers and a new aluminum radiator, etc. Looks like a good motor for a build, and a decent price for it and the stuff he has listed to go with it.