I bought a set of new-never-used Iskys in the 80’s off of a local Mopar guy for $100. Rockers, adjusters, separator springs.
I already had a set of Crane iron rockers on my 440 at the time, but the price was right.
Fast forward about 15 years and I dig them out to use on my 383.
The bodies were much wider that the Cranes, which made the tip to valve alignment way off, plus the the space between the two rockers was greatly reduced, to the point where the separator springs wouldn’t fit between the rockers.
I used an old Crane rocker as a template for where/how much to whittle down the Isky’s.
They were pretty chunky too , compared to the Cranes, so they went on a diet.
It’s the only set of Isky’s I’ve put on anything, and don’t know if the width issue was because they were an early set or what.
They probably would have fit an early set of heads that used the aluminum bolt on stands, which as I recall are narrower than the stamped shaft hold down clamps of the later heads.