Thanks everyone for the quick and thorough replies. Looks like I have as about as much information know as can be had without trying it. I do like the option of using INT0 just to wake as member johnwasser suggested and of course the only downside is the use of a pin that might otherwise be used for additional functions.
One other thing that confused me is whether an event capture would be considered a "timer interrupt"; the overflow and compare match is what I think of as a timer event.
Would another option be to configure the pin as a port change interrupt before going to sleep? After waking I could reconfigure the pin to act as the event capture. I would lose some timing accuracy at the beginning but I am not sure that will matter much.
I am using the Arduino IDA and standard Arduino boards although obviously I am deviating from standard commands. I am pretty much a beginner but learning is so easy with all the resources out here.
I don't get much spare time to work on the project but when I do I will test the options.
thanks again!