USFS was never talking about AH-1's. The Forida Department of Forestry got some over the past few years, and they're working (most sitting). All for longline work.
avbug is not flyingwildfires. I only post under one name, here.
I don't know about putting garrets on the -4; the best upgrade was to go to the super DC-4.
Some serious work was done to make a conversion on the P-2 which would have put Allison T-56's on her. The prototype even went to a glass cockpit. However, lack of funding (and powerplants) stalled the project a long time ago, and there she sits. Personally, I think that's the most promising advent for heavy tankers right now.
The herc was a wonderful airplane to fly, from a tanker trash perspective. It was smooth, quiet, light on the controls, and had ample performance when working in tight, rough terrain. The addition of a third crewmember (FE) was welcome, too.
One DC4 this year had 56 cracks in the spar, on inspection. The upcoming year still appears to be one big question mark.