Hello Don if we are talking about your Mack, then it did not come from Mack with auto slacks. So you could (legally) install manual slacks. Call or stop into a Mack dealer with your VIN# and they can tell you exactly what your truck was built with. Your Mack is too old to have come from the factory with autos. If I remember right it wasn't till 95-96 that trucks were mandated to have auto slacks. A few years prior to that they were an option but since your truck is 10 years older then the mandatory date you should be OK. Another thing to do is to change out the clevises to manual ones. Yes the auto clevis will work just fine, but if DOT checks you and all your clevises are from auto slacks it could cause you to do some "explaining". And we all know how well the police listen when we try to explain. Now if your truck was newer and had come with auto slacks from the factory then it waould be illegal to revert to manual slacks. That is within the USA, I do not know about Canada, or Mexico.
