Welcome aboard and congratulations on your aquisition. Once you get the drive problems sorted, you'll love it!
Be very wary about removing the engine damper. The rubber mount inside the cross piece is a known weak spot if it's not uprated. There is a "dumb bell" reinforcing bar which can be added and allows the damper to be removed safely.
An 053 battery (Nissan Micra) will fit comfortably and has enough umpy to start the car.