HVAC questions and wheel sizes

[5kcstq <5kcstq@codenet.net>]

Hello all,
    Was wondering why the heater in my 87 5kcstq would take a couple of
minutes to start blowing any air?  Also,  anyone know why it would blow
all the air out of the defrost and floor vents?  It seems to be the same
in either "econo" or "auto" mode.  What are the symptoms of a bad AC
Programmer?  I am not really sure how the system is intended to work.
Also,  anyone know what the largest size tire you could put on 16" wheel
and still fit in the stock wheel wells of my 5k without rubbing?  I am
desperately in need of some bigger meats under the thing.  Any ideas
will be much appreciated.
Thanks,
Tim Sexton