Yes. I have considered installing a stock heater in the truck. I've found one on ebay with a 6 volt motor. I've emailed the seller who can put a 12 volt in it.
As for an A/C unit under the seat, I had not considered that. I guess, I mostly wanted to (for about the same price)see if it was worth putting in a combination heater/A/C unit. Plus my wife told me she "wasn't riding in a hot summer parade at 5 MPH unless the truck has A/C!" I'm going to miss her... That was a joke but she really said it! :-)
Anyway, I do not like the idea of changing the original look/layout of the engine compartment but with the non-original 261 motor already in there, it seemed like a good idea to look at the A/C option. I ordered one from Stovebolt web sponsor "American Classic" last night. When it arrives, I'll see what it looks like and make a final decision on A/C or just a stock heater.
Follow up Note: I spoke with them today and cancelled the A/C order as I need to do more research before I spend money I don't really want to spend.