Hey Eddie,
 The moldboard are worth that much. Tires shouldn't be a problem, sometimes bias tires can be found around a salvage yard, just make sure they aren't dry rotted. I know where there are some in Ohio, same guy normally would have a trip for a plowmaster. Why don't you try some 'Gibbs' first, it is good stuff for freeing up parts. I think Wayne Timchuk knows where to find some, his phone number is 419-929-8237. Area code might be different it might be a 937 area code, the phone company in Ohio has been getting silly about area codes lately. But, that is the number I have for him, I know he had some extra 'Gibbs' a while back. If you get some, spray it on the parts, take a ball peen hammer and soundly tap on them to set up a vibration, don't hit hard enough to break something. Do this every day or two, checking to see if the parts are free. In a few days they will free up and work in all likelyhood. If not, get back with me, I'll see if a good trip can be found. You might be plowing before you expect to.
Have a great day!!!
Andy