questions on combining object and fillets

 From:  Jim (JIMCRAFTON)
I'm having a problem combining object and achieving a fillet. I have no doubt the problem is with me, but I'm stuck as to how to resolve it.

I'm creating two shapes from the following outlines:

I'm creating the "wheel" from this curve (highlighted)

Sweeping it

Then lofting the following closed curves to create the "body"

I end up with these two shapes. So far so good. Ideally what I want is a nice smooth transition between the two shapes. Is there a better way to approach this?

If I boolean union them, and try the fillet it either doesn't work, or at 0.01, it "works" but there's all sorts of artifacts. I've uploaded the 3dm file if anyone wants to take a look at what I'm doing wrong. Thanks! The final two shapes are named "body-wheel proto".