Wow. I can understand your frustration.
I received mine in the time frame advertised. I did have a few complaints though:
1. The nuts and bolts are SAE, not Metric.
I have a B2910 that is essentially the same as your B3030. If I remember right, there are two studs and four bolts for the rear wheels. Could be wrong, this is my memory speaking. Do you mean the hardware that is uses to mount the wheel to the spacer is SAE, but the original nuts and bolts are used to mount the spacer to the axle?
2. The nuts and bolts have different head sizes unlike the Kubota ones.
I assume you mean the SAE bolts that are used to mount the wheel to the spacer, are different than the Kubota nuts and bolts that are used to mount the spacer to the axle?
3. The holes where the nuts/bolts go are too small for an impact socket.
Oh well...I wonder if that is due to your spacers being aluminum, or if it is the same with steel as well?
But, they seem very well made. I got the aluminum ones - that's all that I saw. Maybe he had problems with the steel ones (based on your experience) and discontinued them. I ordered mine in early November I believe it was.
I might order a set but only if they are making the steel ones now. The web site seems to offer the steel ones...