the earlier imps had a pronounced bubble effect at the top of the windshield, this was used on all the Imperials from 57-63 and 64-66 on the convertible models only.
the 64-66 imp windshield used on coupes and 4 doors had a flatter slope.
you can use the flatter top windshield on a 60 but it wont have the bubble effect.
my 64 convert had a flatter one until i replaced with a bubble one.