rear end question

[3rdgencharger]

I just got a couple more 73 Chargers and I am trying to figure out what rear ends they have. I have 7 Chargers, all of them 3rd gen, but only one of them is worth keeping, the others will be parts cars. I will have some great parts to sell! One of them seems to be a posi. It has no bolts showing from the rear, and when I turn one wheel in neutral, they both spin the same way. The seller said He thought it was a 4:10 rear end. Can the ratio be gotten by turning the wheels and counting revolutions of the drive shaft or something like that? And I wonder if my brake drums will fit? The others all have the bolts.....10 bolts I beleive. How can a guy know if he has an 8 3/4 rear, open gears, etc? I know I might not be getting the language quite right, but I do not claim to be a mechanic.......just a guy who likes to play with cars! I want to get my Charger back on the road ASAP, so I have some decisions to make! I think I should install the posi rear end.....I do not know if any of the other rear ends have any value to sell. I put a 360 engine with an edelbrock carb......650, I think in this car, but it will not spin the wheels. I wonder if it will perform better with the posi? Thanks for any input that may help me decide what to do with some of these issues!

[oldkimmer]

...............8.75 PULLS OUT THE FRONT, stronger than the 10 bolt cover 8.25..............both wheels turning the same way usually means a suregrip,  .........mark the pinion and the brake drum, or tire on the sg rear, turn the axle 1 full revolution count how many times the pinion turns....eg...4.1 revs = 4.10s.............kim.................