I'm looking for a replacement headset for the no-name one that originally came with my (mid-1980's) Panasonic DX-2000 (Japanese) road bike. I know that it's a "standard" 1-inch headset, but I don't know for certain if it's ISO or JIS. Sheldon notes a difference of 30.2 vs. 30.0 for the "cup outside diameter" but I'm a little uncertain where to measure this. Is this the part that fits inside the headtube? Or does someone know with a high degree of certainty that it is ISO?

Also, I've done my best to measure stack height without re-assembling. So without the ball bearings, the lower cup, upper cup, upper race, washer, locknut add up to about 38 mm, only counting the parts of the cups that are exposed. Seems to me, if anything, adding the bearings would make it a little bigger. So am I OK with anything that has a stack height of 38 or less?

And if looking on eBay, how would one know the stack height of a particular headset if it's not stated? Just a matter of searching the web for a reference??

Thanks.