Back in December, which was pretty cold this year for SC, I attempted to drive it to work one morning which is about a 22 mile commute each way. I didn't make it a mile down the road and as I was going up a slight hill it just lost all power. The truck continued to run, and it would rev up when I gave it gas, but it had no power. It did not stall out or anything. I coasted into the post office parking lot, sat there for a few minutes, then it began driving just fine again. The gauge only said a quarter tank of gas, so drove another half mile to the gas station (it did it again as I was pulling in). I filled up, and attempted to drive back towards the house. It did it two more times within the mile or so back to the house. I jumped in my car and drove to work.
I talked to some of my coworkers, and they thought it might be that I didn't let it warm up enough, or didn't use the choke correctly. This is my first older vehicle, so I'd never had one with a choke before. I drove it couple weeks later around town after letting it warm up for 5-10 minutes, and it seemed to run fine. I just chalked it up to operator error.
So anyway, I got it painted a couple of weeks ago, and I drove it to work and back and had no problems. However, I was driving it yesterday just into town, got about 3 miles away from the house, and it started doing it again.
The truck is a 1967 Ford F100, and based on the site tutorials, I believe it's an FE engine. It fires up every time without issue. It does leak a little oil when it gets warmed up. I'm not sure if it's normal, but the truck doesn't go any faster than about 50-55, and up hills, about 40. When it completely loses power, it's during higher revs -- when I'm either in second getting ready to shift into third, or in third doing about 45-50.
Here are some pictures if it helps: http://picasaweb.google.com/ozolins/1967FordF10002#
I'm fairly new to working on vehicles, and I don't really know people since I've moved to Charlotte, so any help on where to begin troubleshooting would be great. I bought the truck because I love the way they look and I thought I could do some of the work myself without it being too difficult. I'm not afraid to take it to a shop though if I think something's over my head.

Thanks in advance!