A bonded title is usually an option used when there is no longer a path to trace for a title. That's what I did and is mentioned above, and is not that hard. A little costly and takes some waiting time but not bad. Yours may go even faster than mine did if your ID plate is still on the seat riser.
The ID number of mine was long gone also so I had to get the truck put back together enough to have state patrol inspect, once to verify it met the definition of a vehicle and sign an application that I sent in with pictures, bill of sale, and a letter from previous owner stating how long he owned it and how he acquired it. So then the state could place what they thought the value was so they had a dollar amount they could tax for title issue, just like buying a used car. Then trooper had to come again to verify the placement of new vin number that the state issued. It had to be affixed to the drivers A-pillar in such a way that if someone were to try to remove it, they would likely damage the tag, per WI statutes. I just put 2-part epoxy on the back side and screwed it to the wood and the trooper was cool with that.
BTW I bought my bonded title through our insurance company. They charged a fee also but was far less than an online bonding company wanted to charge, I mean like 1/3 the amount, so ask your insurance company if they offer that service if it comes to it. The trooper was free

Just a thought that if you know who your uncle used for insurance carrier they may have info helpful.
'Buying a title' is not even to be considered IMO and as mentioned is illegal! A vendor at a swap meet tried to get me to take that path. He was selling "historical documents"
If the truck was still titled in your uncle's name, and the state still has record of it then I can't imagine that there isn't a path that can be taken to have a replacement title issued and then transferred to you.
It may involve whoever was executor of his estate at the time of his death, not sure.
When I was researching a title for the parts car I had to restore my 67 Cougar (I was thinking of keeping the parts car also), the WI DMV had me request in writing to the state historical society, as the DMV had purged their records of items last titled prior to "X" year, to acquire the status of the title. Turned out the title was 'junked' so that ended that endeavor.
Anyway, I said all that to say that it's very doable one way or another.
I'm sure I'm not the only one who would love to see pictures of the 'old boy' if you get a chance!
David