Is an 8 1/4", 2.45:1 diff housing exclusive?

Just noticed a leaking rear axle seal on my 8 1/4", 2.45:1 rear end. I've enjoyed looking at rear ends my whole life, but never gave them more than superficial guy type thoughts.
:popcorn:

This axel leak got me wondering if this is the (winter) time to swap out the 2.45 gears and do the Jeep rear disk swap. I read an 8 1/4" write up on an early Cuda forum (http://www.earlycuda.org/techdocs/Jeep8.25Swap.pdf) that, "Units with a 2.45:1 gear ratio have a special differential case that will not accept any other gear ratio." Say it 'aint so!
:wtf:

And as long as I'm asking for advise, what rear end gears are people happy with when it's a /6, 4spd. Hopefully this little Dart is on its way to being a daily driver with mild performance mods at the most. Our maiden voyage down and up the west coast shoreline had me downshifting to 3rd every time I met a hill doing 60-65 mph or less. Steep incline starts are a bit of a drag too.

Thanks in advance for the info!:thankyou: