TMI seat foam install in a '67 ???

as a final note here .... yes, I will post pics and details of the seat back "restoration" .... I have already dug into it and, as you might guess, there is more devil in the details .... a couple of quick notes on the headrest install piece .... first, without any real guidance I mentally went through the entire process and decided (would have liked to have said "determined") that the headrest mount should be addressed first (and yes, the OEM lists that anchor the back rest foam have to be relocated -- but more on that when I actually get to that phase of the job) .... OK, here's where the real fun starts and I'll just touch on some "challenges" .... the headrest mount is flat and straight whereas the attaching points are curved in two directions ... also, the plate may block the holes that the back panel clips go into -- or as shown in a web pic, the holes may used for the mounting h/w (bad idea IMHO as the rear panel clips have to go into specific locations -- more on this later too) ..... but the big "surprise" is that the headrest guides, specifically the one that adjusts and retains the height above the seat has a .1" x .1" "key" to properly align that guide to the mount .... problem is, the holes where the guide goes do not have a corresponding keyway -- major bummer ..... so now I'll start the prep of the headrest mount by "machining" in the missing keyways to both mounting brackets and to each hole (there's an upper and lower) ..... then there's another "trick" to ensuring this all works once installed on the seat back and hidden by the upholstery .... I may post intermediate progress (with pictures) as I go through this process ..... BUT the quality and looks of the TMI sport heardrest is A-1 and I'm looking forward to having those installed ..... more later -- 67GTFB