Yup... it'll work, I'm in the process of building a 700c road bike right now too, mine is a fixie tho with a flip flop hub so I had to get creative with mounting the rear sprocket, then I settled with welding the 44 tooth sprocket to the fixed sprocket so I don't need to use an adapter or rag joint.
There's plenty enough room in these frames so the installation of the engine is easy.
The one thing you will need to deal with is the rough ride these bikes have, but a suspension seat or seat post and a suspension stem to take the shock off your hands will help a lot as well as take the full shock off the frame and wheels. These bikes aren't made for rough roads but they do have very rigid frames and forks the wheels aren't as strong as mountain bike or beach cruiser wheels but keeping the bike on pavement helps a lot and the shock absorbing seat post and stem also helps since the springs will compress before taking the weight of the bike and rider when a bump is hit which will also help keep the wheels safe. If you can fit bigger tires on your rims that'll help soften up the ride some too, but you can make the bike much more comfortable to ride. A shock absorbing seat post, cloud 9 seat, and a shock absorbing stem or even a front suspension fork will make the ride really nice, but every little bit helps so you may be happy with just a more comfortable seat or the shock absorbing seat post, but there are the other parts available if it needs more to soften up the ride.