I have a line on a 1971 Bultaco Metrella, it's a basket case with no motor. I also have a line on a 1977? 370 Pursang motor that supposedly ran when the rest of the bike was parted out 10 years ago. Will the 370 engine physically fit in the Metrella frame? Can the Pursang motor be set up with a charging system? I'm already planning a complete engine rebuild, if this happens.