Measure center hole to the push rod end. If that's 1.5 as well then I would say they are 1.5 roller rockers. I know with 1.6 you have to elongate the push rod slot so I would assume the cause of this is a 1.6 inch measurement from center hole to push rod end.
1991 Firebird - 2nd Owner (The slow pretty car)
Stock engine setup with K&N Air Filter
T/A Hood - Pre-'91 T/A tail lights - GTA Emblems
'91-'92 Aero Spoiler STILL waiting to be painted
Headlight Conversion Kit to non-sealed beam setup