for the motor question.....looks like the weld-on tail you have deletes the removable section of frame the cb650 has for engine install/removal. Without that removable section, you have to remove the oil pan, oil pump pickup, and the oil filter housing to install the motor. If you use one of your pictures above and use your "paint" program on your computer to draw lines of the dimensions you're after, I'll measure what the stock dimensions are on mine for your reference.