I think there is an error in the Palo43 PCB label for the 40-pin header. It should read 148.TXD1 instead of 158.TXD1. The gumstix Overo J4 connector reads GPIO148_TXD1 for pin 24 in gumstix developer site - Gumstix Overo: 70-pin connector J4 features Extended Memory Bus and MMC signals.

I just cross checked the OMAP 35x TRM for UART1, UART2 and UART3.

Best regards,