These are old Mark Williams aluminum axles. (DONT USE)
They show one assembly method but the photos don't reflect caster angle which would be built into the locating brackets. (4 link)
The tires have been discussed before, but once again, they were designed for 1000 pound load at 300 MPH. Initially they were made for Don Garlits, but used by lots of rear engine dragsters from the mid 70's to present.
I think for your little light weight Fiat with modified sports length wheelbase you will have no problem. BUT, In my opinion there is way too much rubber, and they need to be shaved and buffed. I have had Vilven tires in the Chicago area do some normal tires, but they cant do the little ones. Since I'm going away from them on my liner (Yep, no more lakester) it isn't a problem for me.
My entire set up may be available if someone is interested. Or not.
Good Luck
Rick