Well, if you could find a speedo calibrator for the vortec 5.7, it'll only run you about $100, but a programmer is around $340.. I know Abbott makes a speed cal for Mustangs (used to have one), but I don't know if they have one for chevy's. You might try asking around at
www.fullsizechevy.com to see if anyone know's where to pick one up, otherwise you'll just have to deal with an overly high speedometer and early shift points (wont hurt anything but performance) until you can afford a programmer...