I purchased both sides for my 69 convertible some time ago knowing that I would need them once I sourced some 1/4s. These are made from strong 18-gauge steel. Looking at them, they look to be long enough, but for the 69/70 at least, they are too short to use as a patch panel without having to add to the length. The 69/70 original part is 25 3/4", and this patch panel is 24 3/8".
Also, the description for this part mentions the 3 raised enforcements. It states the 69/70 raised portions are supposed to face outward. On my 69 and the 70 donor quarter panels that I purchased, the raised portions are definitely faced inwards. Not that it really matters, or maybe a typo in the description, just something to note if you're restoring back to stock. Overall, this is a nice part, I just wish it was about 1 1/2" to 2" longer.