A good place to start is HERE. I found this INFORMATION that might show you what you are looking for. For parts you might want to post an ad in the TRUCK PARTS WANTED Section, who knows what you can find?

There are a few guys on the 'bolt who have the chevrolet Hydramatic and may be of some help. Those answers can be asked in the CRASH BOX SHOP

Tim Lederman put together INFORMATION and I would think it would be helpful to you to visit. I think Tim may be able to show you a delete panel for your heater too.