1970 mach 1 mustang ac cold and hot air

I replaced the compressor/clutch,dryer and the expansion valve. Vac'ed the system and charged it with 2lb's of R-134. the ac works great up to the fire wall.There is hardly any cold or hot air coming out of the vents.The blower is putting out plenty of air.The box was replaced also by the owner before me.
Please explain what you mean by " the ac works great up to the fire wall."
. all of the lines are really cold. the expansion valve is at the fire wall. The air coming into the car is cool, not cold.

If the suction line coming out of the firewall is ice cold, then your gas system is working fine and your problem is in the air control on the inside. Get something to totally pinch off one of the heater hoses at the firewall and see if it gets cool inside. If it does, then your having a problem with heat getting mixed in. I'm pretty sure they used a water control valve back then so make sure it's shutting off.
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o.k. I'll try that. there are vacuum modules in the air box also. what I need is a break down of the ac/heater system. any ideas where I could get this?
It's going top be tough for something that old. My database only goes back to 82.
Try searching for a service manual on E-Bay.

o.k. thanks for your help. I will let you know the out come.