There were ashtrays in OH-6's, OH-13's, UH-1's, AH-1's and all others I am aware of. No they did not reek of fuel fumes (mostly JP-4) Yes, I smoked in flight enroute to or from operations. CH-53's had turbine engines and used JP series fuel (JP-5/6?)
Never saw a power line in Vietnam but hit a couple of telephone lines.
Smoking was not my major concern. All those people shootong at me was my mian concern.
Hugh