if you pay scrap value (and I can't imagine paying more) - you really don't stand to lose much. If you can't find the parts, just scrap it.
John Deere will often surprise you with old parts in stock - and any dealer can typically find them right away for you - but they also very often tend to surprise you with what they expect you to pay for them.
Before committing, just stop into a dealer - they'll have the parts catalog if you know for sure what model/year it is, and you can at least find out.
If you're in love with an implement, that can be the way to go.
Otherwise it's scrap yards and the internet.
I can almost guarantee you WILL eventually find what you need if you're determined enough.
But to me - unless you have a good source and are familiar with the market, you're going to either spend a lot of money, time, or both.
I stay away from projects that are missing major components like that. I figure I can pretty much FIX anything - but there's usually not much you can do about missing parts.
If it's a fun little side project that's one thing - but if you're looking to use it this spring, I'd pass, and find one that at least has all the parts.