looking for A/C cab tech info/ cowl area

[madcow75]

Okay I have a 1976 non a/c cab which I am converting to a/c. And I have 2 questions.
-Are the holes in the cab where the kick panels located, (outside air flap diverters) are they there on an a/c cab. Or could I weld them up. I was looking at the LMC catalog and the drivers side kick panel appears to be solid.
-The cowl area on the cab where the screen is. Can I smooth that out and weld it solid. Or are they required for heater/a/c operation. I do understand they are there to access the wiper arms, but I would deal with that if I had a problem. My biggest thing is leaves and debris getting in there and rotting out the cowl area of the cab.
I just got done welding up the swiss cheese type cab area next is por-15 the snott out of it. I don't ever want to see it again.lol