You need to go to a tire shop and find out the "front axle ratio". They have a book that gives that number on all tractors and from that you can divine how the front tire will pull in relation to the back. The number might be in that code on the above plate but I don't know how to read it. A shop manual at a New Holland dealer will also likely contain the info. My 85 HP 5520 Deere was around .74.
I have the math on how to use that data with the rolling circumference of tires and how to compute the correct tire sizes. I'll look for it and post it but I got it from a Firestone tire book. You want the front to "pull" the back from around 2% more to maybe 4% or 5% more.
Another good choice is to simply go with the tire combo offered when the tractor was new. I think it's 18.4-34 rear, as you state and the front sounds correct as well. They made a lot of these and they were likely all the same. Wheels should be no problem. Tires on those used wheels will all likely not be good or the tractor would not be up in a boneyard in the first place. You'll likely have to find used tires separately at a tire shop or just pony up for new ones.
Tires are not cheap but it pays to buy good ones. I like Firestones because I've never had a problem with them and I like the tread pattern and tread depth. They seem to out pull other brands. For radials they are excellent as are Michelin but I don't have experience with them.
This is an easy project. Find the wheels, sandblast and paint and then wait for the tires to find you. Life is to short to not have what you want.
After all that, tires and wheels are a subjective thing when it compares with raising and paying for a family and all that goes with it. There are priorities and you could easily spend a couple or a few thousand dollars without a lot of trouble.