Rims & Tire Noobe questions

[tri5-73dart]

Hi,
To many of you these questions might sound stupid but I know there is a lot of helpful people here who can help me out.
First off I get very confused when it somes to rims and tires and do not under stand them at all.

Now for the questions.
Right now I have a completly stock 1973 dodge dart swinger. I plan on upgrading some but nothing crazy. So the rims and tires would have to fit in to the stock location.

What I was wondering is if these would fit my car,
http://cgi.ebay.com/ebaymotors/17-PO...21783957QQrdZ1

I know the bolt pattern will fit,(right now I have front disc and my bolt pattern is 5 x 4.5) What I am not certin of if the back spacing and if the bigger rim will fit.

Also what tire size would be recomended.

And lastly, I was wondering if anyone know where I can get a different center peice so that is is nothing mustang, or would I would have to get them custom made.

If you guys and gals need me to take any measurement I can do so.

Thanks for you help,
-Mike