70 390 AMX "Racer" Serpentine Belt Kit

Just received the kit and have a coupla questions . . .
1) The kit consists of alt pulley, crank pulley, and wp pulley, plus an alt brkt and some offset spacers. No idler - shouldn't there be one? How is the tension set?
2) what length or PN for a serp belt is correct, as the kit doesn't include the belt?
3) does anyone have any photos of an installation of this kit? I see other photos of kits with the AC and/or power steering, but this kit doesn't cover those and i don't have them - just the crank, wp and alt needs to run. Pictures would be super helpful!
Thanks to anyone with advice!
Doug