I was able to remove my plastic quick clamps with a 3/4" disconnect tool like whats used on the fuel lines (mine is a Lisle p/n-37000, pkg of 6 sizes) it seems the nipple the plastic clamp attaches to is 5/8" o.d. and the plastic barb is 1/2" so in order to attach the 1/2" rubber coolant line to the alum. core nipple you will have to stretch it over the 5/8" nipple which could create another problem down the road should the rubber line split from age and tension etc.. I've relented to just replacing the plastic connector and hopefully being good to go for another 14 yrs.
I would recommend first cleaning the area good if yours happens to be caked with dirt etc. from your use environment. Then prior to inserting tool rotate the clamp a couple times and push it back toward the firewall by hand or pliers, then insert the tool working it into the back of the fitting. You may need to wiggle the fitting slightly to help the tool start as your pulling tool into the fitting with your finger tips compressing against your palm/heel of hand (unless you happen to have some kind of handy dandy tool that would fit around the tube and compress the tool into the fitting) hand/grip strength is very helpful here and mine is for shit so it took a while along with the customary cursing etc until being able to fully bottom (aka balls deep) the inserted tool into the quick conn. fitting. The inner most core barb is pretty easy to reach to/around etc. the other one, the basstard leftist that it is, (political humor) is a little more difficult due to it's position between the other barb and close proximity to the angle of the firewall but it's still doable just takes a little more patience. On this one I had to sand the inserting edge chamfer on the tool to a slightly longer angle to help it get started. Once the tool is inserted and tabs released pull-n-twist on the connector only.... until removed, leaving the tool in place, then remove the tool. There is a alum. sleeve ring that
is on the nipple that the tool hangs up on. When installing the new Q. Conn. it would be a good idea to lubricate the internal o-rings and alum. nipple with trans fluid or some other lubricant that will promote o-ring life and prevent potential damage to o-rings during installation. For the efficient worker it would take about a half hr. to complete, it took me a little bit longer. Good luck, I hope this helps somebody, happy motoring and HAPPY NEW YEAR!
