Removal of heater box without removing the inner fender on a 67-72 C10?

[BRL]

Originally Posted by HO455

...There's also the hack method a PO used on my Burban. They cut the end of the heater box off, replaced the core and silicone it back together. I don't recommend using that method.

I watched YouTube videos on that procedure and I think that is just so slick!
Maybe run a vacuum hose with a slit in it around the parameter for a seal and some snap buckles to latch the cover in place.
Problem is my heater core is probably the 55 year old original so it's not subject to frequent replacement.
May never get the opportunity to tinker with that thing but I sure want to.