Good morning Ken,

The USPS V3 last updated by Ajeh is the most current and supported USPS module. You can try using the language file from Ajeh's V3 version with RateV4. I haven't a clue whether full functionality will be achieved or whether it would be considered stepping on toes since you would be blending 2 competing versions. The RateV4/IntlV2 has not been confirmed as functional in V1.5x but it does offer a more enhanced option set.