Whatever you do, do not use the original rod brakes for an electric bicycle. Especially if you are using a 48V pack!
Use drum brakes, you won't have to drill holes in the frame, just get the right mounting hardware (If you are lucky, you can score components that let you use drum brakes with the original rod linkages. Gazelle still makes bikes with rod-operated drum brakes. I use one as my non-electric commuter).
I don't think the Flying Pigeon is a good candidate for a hub motor. The front fork is at too slack an angle for a front motor (At least for my feelings of safety) and the rear drop outs are not solid
steel (see above posts). There are better machines to electrify, although I occasionally muse about converting my pigeon to run slowly with a 24 volt system. I'd recommend getting setting up something chain driven. Looks more retro, and doesn't put so much stress on those rear forks. That being said, I might put my s-l-o-w Heinzmann hub motor (13mph tops) in there and report on it.
If you want more info about motorized classic roadsters, this site'll suit you http://cyclemaster.wordpress.com/
Again, the original rod brakes are really only any good below 17 or so miles an hour in the dry. And I mean bone dry.
I am not trying to discourage you (plenty other folks on this forum have tried to discourage my forays into the world of flying pigeons) but use yer loaf, play it safe. These frames are strong, but perhaps not electric strong, and probably not 48 volt strong
Not all hub motors allow you to use a drum/band brake though. you might have to ask a local shop to drill holes for side-pull brakes.
Anyway my recommendations boil down to..
1)DON'T USE THE ORIGINAL "BUTCHER'S BRAKES". I know they are sexy, but you don't want to get intimately acquainted with cross-town buses.
2)A chain-driven solution might work better, and allow you to use different gear ratios with your motor. It'll also allow you to use Sturmey Archer's excellent drum brake rear hubs (3 and 5 speed)
3)If you must have a hub motor, they are pretty convenient, see if yours has a drum or band brake, if not, get a local shop to drill holes in your precious frame suitable for the best side-pull brakes money can buy. That's for the rear. Use a drum brake for the front. Period.
4) You will cry because this endeavor will take ages and cost money, but it is a very nice hobby once you get into it, and you may find yourself eying every bicycle around you and contemplating whether it can be electrified too. Welcome to the forum.
5) Ask a good machinist whether your bikes' rear forks are ready for this task. Reinforce them if possible.
"I'm not the smartest fellow in the world, but I can sure pick smart colleagues."
-Franklin D. Roosevelt