273 Crankshaft Quiz

Not really a quiz, just a whole lot of questions that I'm numbering to reduce confusion. I'm confused enough for the whole forum. I have a 1965 Barracuda Formula S with the stock 273 4bbl and a 904 automatic. I've been trying to figure out what my options are in terms of engines/converters/transmissions if I decide to change anything, and it all keeps coming back to the '65 273 crank. I have several questions that I haven't been able to find answers to in other threads.

First, some basic questions:
1) This is a six bolt crank, right?
2) An automatic car crank only works with an automatic without drilling it, right?
3) Can I use a modern timing chain and harmonic balancer with this crank?

Other threads have said that the early 273 cranks use a smaller "hub", "pilot", or "register".
4) Do all these terms all mean the same thing and refer to the big hole (technical term) in the crank rear flange? What term should I use?
5) When did they switch to the larger size?
6) Would running a newer engine/crank with a larger whatever it's called prevent me from using the original 904 or the stock converter?
7) Alternatively, can I run a newer converter with the 273 crank?

Answer any questions you want, any way you want. I can use all the information I can get on this!