Arduino UNO + Arduino GSM Shield + Sparkfun Venus GPS
I received my logic level converter today and wired it in between the Venus GPS and the Arduino GSM shield. 

The issue seems to be resolved and I'm able to properly receive information from the TX on the Venus GPS.  It would seem that my assumption was correct and I needed to "step-up" the 3.3V TX signal from the Venus GPS in order to use it with the GSM shield.