How far away does exterior gas dryer vent need to be from elec. outlet?

The only consideration you have is not to cut an electrical line in the wall when making the hole for the exhaust vent. Proximity to an electrical outlet is not mentioned and the reason is that the gas has already burned at the exhaust end and is not explosive. Thinking about it that way, doesn't it make sense that there is no regulation. The second thing is that you have an outlet the gas dryer is plugged into inside right now ( or you will) which is the power for controls and to turn the barrel of the gas dryer. If there was no outlet close enough to plug in the cord you would have to bring one in and that is usually right near or behind the dryer where the gas supply line and combustion chamber is. You are fine, just be careful about cutting the hole.

You can research the building codes through your city's city hall web site. I would tell you but my drier is electric.