8-1/4 Ring, pinion, diff change on 1969 charger

[brianosaurus]

I ordered a new ring & pinion and an auburn gear for my 8-1/4 rear end.

I've read throug the install instructions that came with it, and they're OK,
but when I looked in my 1969 Charger (year-one reprint) service manual,
it only has the 7-1/4, 8-3/4 and 9-3/4 rears, so I don't have a source to fill
in the gaps.

Is the 1969-ish 8-1/4 similar to one of the others?

From some of the pictures in the installation instruction it looks like there
are threaded adjusters to hold the carrier, rather than a shimming solution
from side to side.  Is that what I'll be looking at when its on the lift and I take
the cover off?

Also my diff cover doesn't have a plug for adding oil, but I think I saw one
on the passenger side of the case.  Is that right?

Any other tips for installing this stuff?  I'm hoping to put it in this Saturday, so
I can start laying 2 black stripes everywhere I go. 

Oh yeah..  While its up on the rack, is there any play between the axles and
the leaf springs?  If I hit a decent bump, the rear-right tire rubs on the fender
chrome trim.  There's only about 1/2" gap between the tire and the trim when
the car is sitting.  There's probably an inch or so clearance on the other side.
There's like miles of gap (like 6" or so?) behind the tires.

I'm planning to get new wheels & tires, so I can go smaller.  The current ones
are ~28"... 275/60R15.  Are they just too big for stock, or is there a way to move
the whole axle back just a bit?