Get your TIP and FMM online at
https://www.banjercito.com.mx/registroVehiculos/# and
https://www.inm.gob.mx/fmme/publico/en/solicitud.html# TIP arrives in 11 days or less and can be purchased up to 60 days before you cross. Just place on your windshield and sign the paper back it came on. FMM can be purchased 14 days before crossing and prints out on YOUR printer. You have to stop to show ID and get it stamped. NO money exchanges other than what you pay online. Much easier.
Hwy 54 is a beautiful drive but there are some narrow and steep sections as you near Guadalajara. We did it pulling a 37' fifth wheel with no problems, just don't hurry.
rocmoc n AZ/Mexico