Why do two different ICs have wildly different high level output voltages?
The logic family specification defines min./max. levels for H and L output states.

As long as both ICs satisfy the specification (which I assume is the case; i.e. in this case voltage is above min. H output Level 2.7V) there is nothing to wonder about.

The output voltages don't have to be exactly the same; they just have to be above the minimum level.

See e.g. \$V_{OH(MIN)}\$ "minimum guaranteed voltage at an output terminal" here.

So after it is clear that they don't have to be the same: here are some reasons for them not being the same: 


different temperatures (maybe even different elevated temperatures sometime in the past; e.g. by overload)
output circuits inside ICs differ for some reason (e.g. because they have different max. fan out)
ICs are made by different manufacturers
ICs are made in different process technologies
ICs are made at different plants
ICs are made at different times
IC dies come from different wafers
IC dies come from different parts of the same wafer
...


The answer is similar to the answer for "Why may \$\beta\$ vary so much for two samples of a BC547C transistor?"