Looks like 4" bolt pattern for sure.
If you go with a tire wider than 8" you'll want a backspace of 4" or less.
It might be 4.25" from the drum face to the spring but the tire sidewall bulges out passed the wheel bead edge.
Now the you have the wheel off... measure from the drum face to the leaf spring.
This 'deep dish' wheel would work fine but finding a match will be a needle in a haystack.
