If you flash back to the 60's you've went to far :wink: Gotta put the brakes on when you hit 1970/71 to see that bike. It is a Bonanza MB 1210 original power for the centrifugal clutch version like yours was a Tecumseh H35 3.5hp. Currently a company called Coker tire has a goor repro of the 4.00x6" tires available like that had if you are doing a resto. If you have access to a media blast cabinet that the tire/wheel will fit in, I find I have the best chance getting the phillster head bolts to come free and not damage the bolt or more importantly the threaded halve If I glass bead around the head of the bolt and the threaded end on the other side real good to clean and dirt/rust I can off the threads etc.. You can even do an initial clean of the wheel and even tire at that point and get around the lip a little where tire meets the wheel.
Once cleaned up a little I use an impact driver and give a smack on the head to work them out, Some will pop easy if the threads are clean enough, if they bind I keep working them back and forth half/full turn a few times and try to work them out a little farther and repeat. Sometimes you cant avoid snapping a bolt in those wheels if they are really corroded, but getting those exposed thread really cleaned up and using an impact driver has put an end to any broken bolts for me on those particular wheels in the last few years.
I have assortment of automotive repair style prybars from screwdriver size on up, I use those to help break the tire loose, carefully wiggling one in between tire/lip as far as I can and then a little twist, gotta sometimes go all the way around as the corrosion can make the stick pretty good sometimes you just need to do it in a few point around the lip to get them move.
Good luck with it, looks like its in pretty solid shape and been hacked on.