somethings wrong with me . luck of the draw?

The rear will fit if you relocate the spring perches, but it will be wider than the factory A-body rear so consider that when it comes time to get wheels. The 413 should fit in with minimal hassle with all the conversion kits that are available nowadays. Do some looking around here for the big block swap. Plenty of guys have done it. That being said, it's not every day you see a '65 Imperial. If it was mine, I would try to keep it original and make it a driver.