The LSTTL version will be fine as long as you're OK
with about 400uA IIL.
CMOS versions will see elevated Idd / Icc with weakly
driven inputs, a 26CT31 would be better than a 26C31
due to input buffer design but still may end up with
higher Idd at Vin=3.3 (or 3.16 or 3.0) than the TTL if
the '31 front end is held there.
You may find (though fewer) CMOS 3.3V RS-422 drivers.
They have a hard time with loaded output difference at
low temp due to the blocking diode / Darlington emitter
(depending on whether CMOS, or TTL technology) but
that's more of a spec-marginality than a functional impact
kind of problem - a slight miss on noise margin, like 9.5:1
instead of 10:1.
And it's likely that your 26LS31 could run "OK" (less drive
but perhaps adequate) at the same 3.3V rail. You may not
have a spec table for that condition, but might find that
has been characterized at some point.