Originally Posted by
streetcore
unfortunately I have bigger problems to worry about since it looks like I ordered the wrong headset.
The eBay listing didn't show a drawing with measurements like I just found online and didn't list the cup size, but did say "S.H.I.S Upper: EC30 S.H.I.S Lower: EC30". I wrongly
assumed this meant the cups were 30mm like my old ones, but the new ones are actually 30.2mm.
Assuming you can't return the headset for a proper size replacement, it's fairly trivial to mill a 30.0mm ID head to use 30.2mm headset parts.
If it turns out your fork is the mutant 26tpi steer tube thread, you can install the new lower race and keep using the original upper race and threaded parts as long as the stack height is reasonably close. Upper headset races seldom wear out, as the lower race bears all the load while the upper race only serves to hold alignment. In that case, you'd only want to mill the lower head tube to accept the new parts.