I'm reconditioning a 1970 Fiat 500 that has had a front disc brake conversion. I am attempting to replace the front knuckles but they are no longer from a Fiat 500 and appear to be a Fiat 850 part. As I search for a replacement, its clear there are some difference between the 850 Special and the Coupe/Spider.

http://www.ricambio.co.uk/69-fiat/5...set-of-stub-axles-steering-knuckles--fiat-850

http://www.ricambio.co.uk/69-fiat/5...s/1351-stub-axles-steering-knuckles--fiat-850

The response from Ricambio is that the "...difference between the Stub Axles on the 850 is bearing size of the shaft." He suggests a kingpin repair kit instead but am famously lazy and would prefer just to replace the part.

Can anyone expand on how I might determine which part I have?