[48richard]

I have not gone from A/C to heater, but I have done it the other way round. The openings in the firewall are different, but it's not a difficult mod. You will have a couple of extra holes where the heater hoses came out - with A/C the heater is inside the cab, and with heater only the heater core is in front of the firewall. You can see the difference in this picture. The paper pattern is what I needed for A/C, so your truck should look like that now. The large opening towards the center of the truck is the same, but the other large opening needs to be changed, and part of it will have to be blocked off, I think, because the heater box will not cover it. Hope this helps.

Richard