Motorcycle build: High School Shop Project

Hi guys, I am a high school metalworking teacher and I am in need of assistance. I know just about nothing when it comes to motorcycles and dirt bikes. My students are building a replica 1910 board track racer. We have built the frame, tank, front forks and now we are getting to the wheels and power plant. We used a 1982 yamaha xt 125 and I have a question about the wheels. On the bike, the rear wheel is a lot smaller than the front. On our build, we want the wheels to be the same size. So, I would like to take the hub/sprocket and put it on the same size as the front wheel. Is this as easy as it sounds, or will this be a headache? I’m guessing the only thing we will need is longer spokes. What are your guys thoughts on this? Thanks!!
Andy K