I would cut and thread where the machine is and then carry the pieces down, much easier. A bit of walking is better than humping that thing around. Get your measurement, calculate the pipe length, then go cut your threads. I'm sure you know how to check and see if it's cutting right, spin a fitting on and you should get roughly 3.5 turns by hand, dry, that's how you set the dies (3 to 4 turns is usually close enough). And i would use both pipe tape and dope on them, that makes them seal better but they will be more likely to move around more, so make sure they are well supported. And a ton of never sieze on the union faces and threads, otherwise they will rust together and you'll fight like hell to get them apart again, and the faces might leak without it. Buy any shorter nipples you need 6" and under, if you don't have (or know how to make) a nipple chuck you'll fight them because you'll mess the threads up with the vise trying to hold them when threading. I prefer to cut my own because I'm particular like that, but for most that's too far for most applications.