Would like to replace my tub/shower faucet without replumbing . Is there a kit and how do I find my model number?

Would like to replace my tub/shower faucet without replumbing .
Not possible to replace without doing some plumbing. How difficult depends on lots of things. It may be able to be rebuilt if that is desired.
Post picture of faucet.

Agree but first tell us why you are wanting to do this, isthere a problem with the old one?

What tub and shower valve. Do you have now? Is it a one handle or a three knob .
Valve? What kind of pipes? Galvanized, copper or plastic? What do you wish to replace your valve with? Can you give us more details? Back to you, Tom

Some manufacturers, like Delta or Price Pfister offer conversion kit from old style to new 1/4 turn handle style. Not every faucet fits this conversion but some do. Check with the manufacturer. Otherwise, you will have to cut out the old body and install new one.

Hope that helps. Milo