I really would prefer to stick with a 3-4. We're pretty well geared up for such a scheme. If we MUST run a 4-3, we want to run a 4-3 UNDER, not over. 4-3 under is basically a 3-4/4-3 hybrid and more of our guys would just be drop-in replacements.
At the end of the day, I don't a wholesale scheme change is necessary. Our front 7 is pretty good a stopping the run this year. That won't change much unless we went to a pure 2-gapping scheme, which would be a mistake. The glaring problems are pass rush and cornerback.
You can run just about any coverage with any base scheme, so 4-3 vs 3-4 doesn't matter without better corners.
Ditto pass rush. We just don't have a really special edge rusher anymore. Perry is pretty good, Matthews on the downslope and approaching "above average." With no one demanding a double team at least "most of the time," opposing offenses just double the most appropriate per alignment and playcall, with the assumption that the other guys can handle the other rushers one on one.