Matt,
Relative to "pushing" the center offset: Some years ago (maybe 20) I found that there was an offset difference between 4-bolt and wide-five wheels. Actually, quite a bit of difference. So on my spyder (a 718, not 550) the wide-five wheels in the front to replace the 4-bolts were offset too wide for the body.
I sent the front wide-fives to: Stockton Wheel
They cut and pushed the wheel centers to my offset specification, which was about a 3/4" push on 4-1/2 wide rims, as I recall. The cost at the time was not exorbitant. I don't know if they still provide this service, but this might be an option for you to look into.
And, I may be mistaken but I seem to recall that Special Editions' (Beck) "Mangles" had a custom offset as a matter of their standard production. You might want to give them a call for possible over-the counter solutions.