It's the blower motor that's kaput, right? HVAC motors are standard in specs, you just need the specs to find a replacement.
Pull the motor and take it to a local HVAC supply vendor or motor shop. They may be able to match a replacement for you.
If that's not an option, look for a nameplate or decal on the motor. The specs you need should be on the nameplate. Not a manufacturer's number, you won't necessarily need that. You'll need horsepower, frame size (if listed), RPM, voltage, shaft size & length, rotation direction. Mounting bolt configuration is important, too... there are variables.
Go to grainger.com and use their search feature. It allows you to drill down by motor specs, making what you need easier to find.
Hope it helps.