I have noticed that trans fluid is leaking from the rear seal area of my 4speed trans in my 70 Charger RT.

The trans was supposed to have been rebuilt and the rear seal looks new.

What else could it be besides the rear seal when you have a leak in that area of the output shaft?

Vent could be plugged up. Drive shaft too short. Yoke or bushing worn. Wire could be off the seal.

Is the vent hole of the trans seal supposed to be pointed toward the ground when installed or should it be on top toward the floor board?

The driveshaft is new and the splines on the trans look good as well.

I do notice that there is a rip on the inside rim of the seal.

it should be on the bottom ... 99% , that way when the seal goes it will leak and tell you the seal needs to be replaced , the outer boot is a DUST SEAL , not and oil seal .

Ripped inner seal , meaning the lip seal inside ? If so you need a new BOOTED seal .