Someone has drawings they can post - otherwise it's hard to describe. If your car has P/S and A/C, but no smog pump, something in the 83"-84.5" range should work depending on whether or not you have stock pullies, underdrives, etc. I just bought 3 belts -- 83", 83.5", 84" -- or something like that. I used the one that fit and took the other two back. Each car is a little different - no one's gonna be able to tell you exactly what length to use on yours - you're gonna have to figure it out for yourself.
Mine is routed from the alternator, down to the bottom of the crank pulley, around the crank pulley to the other side of the water pump (it will hit the water pump pulley at about 8 o'clock, and the back/smooth side of the belt drives the water pump pulley), off the water pump pulley at about 2 o'clock and down to the power steering pump, up to the a/c compressor, under the tensioner and back to the alternator.