Found my dads original 1971 duster!
There are others here who have a lot more experience than me. I have an area or two of knowledge and a bunch of learning the hard way.
H'm. OK. If the carb hasn't been taken out of the box, then this will be a bit different story. How about the distributor and ECU? Did they come with engine? Did he use them on the dyno? Even if the distributor is on the engine, if the engine is going in from up top then in my experience it will be removed during install. Mark the base of the dist to the block as well as the rotor position. That will get you close when reinstalling.
If both the carb and distributor are going for the first time, you and the builder are going to have to do a little reading and/or get some one with experience to give you a hand. The stuff I'm writing about will more sense when you're working with it. At least with me it takes both hands on and reading about how it works before it starts to make sense. Get the cam info and compression and we can make a ballpark estimate on initial timing.