Great stuff here! I've got the same gurgling, but I see air bubbles in the overflow reservoir. Going to replace the engine soon. Would this be a good time to replace all of these hoses with the new ones and the Dorman connectors?
I'd replace hoses, but I doubt I'd use the Dorman quick connect.... should only be one, at least on my 454. I like my brass fittings. I replaced the heater core fitting (instead of the quick connect) with a GM part that is supposed to be for a thermostat by-pass, although I'm not sure on the application. It was something the local parts dept. guy looked up for me. It's not a factory part for my truck (could be for a Mk4 BBC) For the other two fittings, I've got one oem that is the style with no hex on it, and the other is an industrial part from Fastenal.
I'd only use the Dorman part if I wanted some combination of "factory look" and the restriction for the heater core.
The Dorman heater hose that would be the replacement to go along with that Dorman quick connect, is a lot more expensive than a piece of US made bulk hose, and it'll be from China.
If you check Summit, you should be able to find some other options, too. You just need the right NPT thread, and hose size.
Good clamps will also be needed if not using a quick connector, or if you're retrofitting new hose onto the OEM tube that goes into the quick connect.... the other option to the Dorman heater hose.