I just replaced mine last week and used this one from Inline Tube. https://www.inlinetube.com/products/inl15043 It's an exact fit and also much beefier than the OEM one. You don't want a 53 year old original anyway. That cable is the one that always breaks and if it isn't now, it will be once it starts seeing use.
Brett, I was just looking at their site I see Pontiac and Olds sets listed. Did you use one of these?
I used this set when replacing mine. Don't think they sell individually buy maybe you can call them: https://www.oldairproducts.com/product/26-1370-ez-slider-cable-set?gfid=p118168-c145134
I’ve used a lot of Inline Tube parts for my Oldsmobiles over the years. They have brought a lot of items to market that were not available before. They also make my 1/2” stainless pre-bent fuel lines for my Olds and Buicks.
Inline Tube is owned by the Kryta brothers. One of them collects Pontiacs and the other collects Oldsmobiles. Some of the parts are also the same for Buick and even Chevy.
The In-line Tube one seems to be longer. Unless I bought the incorrect one as a spare for myself. I installed an OE one today in Utica Geoff's 71 GS. I'm not saying the In-line Tube one won't work, but just beware that it's longer.
I honestly didn't bother measuring them side by side. I was more concerned with how I planned on accomplishing this menial and annoying task - while on my back - without breaking anything else. I hope the OEM one you used still has some good life left in it because I know I don't have to tell you how much of a suck job this is. Mine fit well and I can hear that blend door opening/closing. I call it a win.
The blue cable breaks because of the nasty turn it makes, or the mode door is seizing. It controls the mode only, meaning either heat or defrost. From "heat" to "off" on the top lever, the blue cable is stationary and another cable closes another door. If that door is sticky, you are likely to damage the heater control unit before breaking that cable's ends. But I'm glad the In-line Tube one works, as the blue ones are in short supply. I haven't seen an intact original blue cable in a long time, and Geoff was lucky to find one.
The blue ones are always the first to turn into toast, for reasons you've mentioned. Geoff is lucky. Actually, a friend just gave me a whole non air heater control box last month with a very nice blue tabbed cable. I think it came out of a 20K mile car 20 years ago. I'll stick with what's in there now. That job sucks.