Ah I see what you mean, so the Pic must be at 5volts.

What about a buffer chip such as 74LVC07A running at 3volts?

http://www.semiconductors.philips.com/pip/74LVC07A.html

Dunno if this will be fast enough depending what speed you are clocking the data in and out at.

Should think the Pic will be happy with 3volts as a input to show a high and your concern is just isolating the 5volts going back to 3v part.

Regards

Sean.