Stop in for a cup of coffee

Mike that thread I always get questions on

Hello,
Maybe you can help me to bring the information I need to a point. I have completely read the 8 1/4 thread, but my English is not so good that I understand all connections.
I've got an 8.25 axle out of a mid 70s with a 3.23 ratio in my '68 Valiant now I've read that the trac lok of a DANA 35 might fit.
I was now offered by a Jeep XJ a DANA 35 Trac lok with 3.55 Ratio.
Now my questions:

- Does the Trac fit into my axle?
- Can I keep my 3.23 Ratio?
- Do I need special bearings?
- are there disadvantages if I install the Trac lok?
Wow, I guess you told him the low gears may not fit his housing ?