Hudson,
The biggest worry using nitrous is getting the fuel pressure correct. Nitrous is just an oxygen carrier. You must add additional fuel to get the correct air/ fuel ratio. The biggest downfall for a lot of users is they try to use a stock fuel pump to deliver the extra fuel and it's not up to the task. The result is a leaned out mixture under extreme load resulting in a blown head gasket ( best scenario ) to a groove torched between the cylinders ( worst scenario ). You will definitely need an electric fuel pump and regulator. The less an engine is able to breathe, the better they respond to nitrous, so it would seem like a flathead would be perfectly suited to it. Power levels probably won't be enough really to hurt anything. You might want to consider a rev limiter just in case something breaks elsewhere though.
Regards,
Del
