I'd mount it and check your chainline. If it's close enough to 43.5mm and you like the way the left arm looks (the Campi may not have been symmetric, but the Shimano is), then ride it without worry.

Here's another question - Campi adopted ISO in '94. Is your 8s crankset pre'94 or '94+? If pre, then your JIS would actually be "closer" to the pre'94 taper than would a modern ISO. (as per Phil Wood's advice)