Any truck that has sat for any length of time (1 year or more) should have the tank removed and flushed.
You know the engine runs fine with a good fuel supply, and you're going to put this stuff in another truck anyway, so why bother with it?
Just use a new fuel line when you swap the stuff into your '65, and flush the fuel tank before you put it in.
Crud in the tank is bad news.. it can gum up your lines, jack up your fuel pump, and clog up your carb.
New fuel line isnt expensive.. I use that thick rubber hose stuff that has FUEL LINE printed on it.. all the auto parts places sell it for under a buck a foot., just make sure you dont run it around any moving parts or heat sources.. but make darn sure your tank is clear before you hook up a new line, or you'll just end up clogging it again.
