Wouldnt apply to you but I find McCarran International terminal to be very well organised.
Immigration and Customs - 10 to 15 minutes
Baggage Collection - 5 to 10 minutes
Bus to Alamo rental car depot - 10 minutes
Rental Car pickup - 10 minutes
Im usually on the road in under an hour from the plane hitting the tarmac. You could well still be in the taxi queue