if i was going to tackle it, i would bend the front part of my chassis flat and put a second transmision on there backwards. then build off of there, modifying bulk heads and such to mount it up well. then figure out how to get rear hubs to mount to either front arms or converting rear arms to the front. then you have to deal with the chain drive and modifying layshafts so that you can put on another gear and run a chain to the front. i would adapt brakes to the front transmission so that you have 4 wheel braking which is a huge +.
just my simple thoughts on how to start tackling the project