Scott:
It may actually be effective for you to consider using a 3.3 volt processor that has 5 volt tolerant I/O's. This can be very effective for two reasons. The processor interfaces directly with the other 3.3 volt ICs. In terms of the 5 volt logic where the signal direction is from the processor to the logic and the logic has a TTL type Vin range from <0.8V to >2.4V then the 3.3 volt swings work great. In the case of 5 volt outputs from the logic to the processor the processor with 5 volt tolerant inputs can permit logic swings on its inputs from 0 to 5 volts without any problems.

All of Cygnals C8051Fxxx type parts work this way. There is a link to a Cygnal app note that covers the subject in a bit more detail. Cygnal AN #011

Michael Karas