I've never owned a governored gasser(except my 66 c60, which I plan to rectify), and I've never lost a motor to excessive rpm. Throw a tach on it, and drive with you upper brain, instead of your lower one. A 327 should be able to hold 4000rpm all day long, under load. Most of the big-block trucks(not pickups) I've drive were geared out to run 4000@55-65mph. I shift my 402 @ 5000, if I'm in a hurry, or showing off.
Keep in mind, oil pressure has a lot to do with the rpm a motor will survive at. I always use 10psi/1000rpm, as my guideline. A buddy of mine that races says a smallblock will survive @ 8psi/1000rpm. I prefer a little safety margin, considering gauge variation, and Murphy's law.