A 73-87 Drop Spindle Questions

[Conundrum]

I found a set of drop spindles the other day, that a guy took off his truck.





3" drop, 1" rotors and he said they take the big bearings.

What are the big bearings on these trucks?
Are the 73-80 & 81-87 bearings different?
If so which ones are the big bearings?



All I knew was a real difference was the rotor thickness.


Also, he said that they are Trailmaster brand. Anyone heard of these or have them, are they a good quality spindle?

I didn't think I could beat the deal of $150 shipped.