Bad news from the tire shop...

[HIGHWAY BY THE SEA]

Today I drove my 67 3500 to the tire shop about three blocks from my house to get an estimate on new tires (which it needs BADLY). The last place I tried to hire to do this work refused due to it having three "widow maker" wheels on it (slang for removable outer rim ring). Well, this shop did exactly the same thing.
It appears that NO ONE will touch these dangerous two-piece wheels due to "people being beheaded by the rings flying off" and other such horror stories. So it appears that I am going to have to find all one-piece rims like the one pictured below before I can even replace the tires. I do not want to take any chances with potentially dangerous wheels anyway.
I need to know EXACTLY what wheels I need to get before posting a WTB on this. I thought I saw a 3/4 ton truck on here being parted out with these type of wheels, but are 3/4 wheels compatible with my 1 ton? And why would this truck come with 3 one-piece wheels, and three two piece ones?
Also, is there any difference in the inner rear wheels as compared to the other four?

Here is the spare one that the Previous Previous Owner was kind enough to give me through the Previous Owner.