The interchangeability will depend on how accurate the SPF is.
Dimensions that I would compare:
Height of the roll bar and clearance to the inside of the top.
Location of the roll bar back-brace and how much clearance there is to the hard top.
Angle of the windshield.
If the top comes unpainted, it's not a big deal to trim or add to the contour where it meets the rear cowl to match the ERA.