I'm not sure about the "downgrade".
The H-272 will almost certainly require head work for spring clearance.
The Crane H-260 is the same cam that came in the HT 3.4 crate motor that GM used to sell. It should work with no head work.
You can figure this by looking at the valve lift. (It's .427, intake; .454, exhaust, for the H-260.) Look at the installed height of the springs, and the "coil bind" height.
If the difference is larger than .454, you should be good to go. (Kind of simplistic, but that's essentially it.)
If you install 1.6 rockers on an H-260, you will have the same lift numbers as a 272 (.454/.480) and will likely bind the springs.
FWIW, the stock Fiero cam and the stock 3.4 cam have the identical lift numbers. (.394/.410)
For some reason, GM liked the "staggered" lift numbers (intake vs exhaust) on their cams, for the iron head V6. I have always tried go go back in with staggered cams. I figure they did it for a reason.