There's a few things to consider to get you a drop-in replacement, or the exact motor that will meet your needs. One is Frame Size.
The frame size is basically the bolt pattern that your new motor is going to sit on; it's related to the shaft size. It's a governed by NEMA standards. Have a quick look at the above image. It's a Tag from a motor and it spells out the Spec's you need to meet.
Here's a typical NEMA chart ...
Here's a handy form that you might want to print out. Work from the left column over to the right column. This will give you all the information you need to best select a motor for your application. Using our website, from there you'll end up with the Model #'s that best fit. And from there you can price compare.