Jack the back of the car up so the wheels are off the ground. Turn one of the wheels by hand and if the other one moves the same way its posi. If it turns the other way then its open. Or look at the tag. There will be numbers on the bottom left of the tag that are for the gears. If there is a "L" in the middle of the numbers, then it is a posi. Mine looks like this: 3L00, if it is not posi it would be like this: 3 00
As for the front end idea..I don't think its going to work. Why would you want to do this anyway?
SVOwagon