Defrost?

[P993C2S]

I've pulled my dash off and I'm eliminating all the brackets,ducts and wire that I can. Next is the AC/Heat unit. I plan on leaving the heater core for now. Looking at other cars online it appears some have a defrost button installed. In Michigan that would be nice on a cool spring and fall morning. Unfortunately is looks like the AC unit provides the fan to blow over the heater core and get the defrost so if I remove the AC unit no defrost. Am I correct in that assumption?

Provost motorsport has a custom defrost listed on one of their cars for sale. How hard is that to accomplish something like that? Is it just fan that blows over the heater core toward the windshied . . . instant defrost!

If you've got pictures post'em please.