Found 8 1/4" Rear End

I found a 8.25 rear end with 245 gear ratio. I was looking at some tech info from some ring and pinion builders. They are saying anything above 271 that I would need to go to a 271 housing before I can go to any lower of a gear.
The rear end came from a 73-74 Duster. I am wanting to put 355's in.
Questions:
1. Was there a clearnce problem?
2. And are all the 8.25 the same?
3. Will I just need a complete rebuild kit with gears I want?
4. What are the steps?
5. And where can I get a master kit?
6. Or do I need to find a 271 housing before I start?

Just some question I have before I get to far ahead of myself.