[AnthonyG]

I’d bet the covers as Henry made them are all the same size. After 80 years who knows what they’ve been thru to deform them. Consider also ur old tire is dried out & probably has shrunk & become less flexible. I’d try deflate the new tire a bit to see if it fits. If it does get a cordless air compressor gun. About the same size as a drill motor & easy to keep in car in case u ever need to use. Not a perfect solution but worth a try. Plus you won’t have to replace the cover. T
Air dragon hand compressor gun is handy anyway to keep other tires @ correct air pressure. Their pretty inexpensive & I have one in all my cars as part of my roadside kits.

Another thing I’d Probably try is deflate a 650-16 more see if u can get that to fit then fill while in cover if you can get to nozzle, to max recommended pressure. Might straighten out the cover enough to let 600 fit correctly. Just a couple of thoughts.