Mark, Just the man I want to see...
Flattery will get you everywhere! I pray you, continue.

We are in the beginning stages of remodeling our hall bath that's about 29 years old. I want to replace existing standard tub with a Claw Foot Cast Iron Tub. Niiiiice.

It has to be less than 52" long. I know that they make them I'm just not sure about a few things. Should I purchase one from over the internet?
Unless you can find them in local distribution (try pro plumbing supply houses/showrooms) or in a salvage shop that rescues such things, the internet might be the only place you can get them (Note: the internet isn't really "a place" per se; I hope you know I know that.

Also there are so many styles to choose from and to consider as far as where the plumbing is located on the wall and/or mounted to the tub itself ?
I can't recommend the type of plumbing fixture you should get because so much of it is subjective. In other words, your starting point needs to be a style you like. Then to follow up and see if that works with your tub, wall, drain situation, etc.

That said, you can make just about anything work. What I can say is what I'd do on my jobs if this applications faced me. Generally speaking I would make sure that if the supply lines were stubbed up from the floor I'd be sure the plumber chromed them. Raw copper just doesn't look good—especially with a chrome or nickel finish on your fixtures .If you choose to route the plumbing in the wall be ready for drywall repair. Finally, make sure you install a trap in the drain; if you don't you risk the smell of sewer gas and/or the aroma of dirty pipe mung escaping back up the drain pipe. Uh... diiiisgusting.

This should get you started. Good luck Vital Vita from Florida!
Carpenter Mark