Has anyone changed the rear on this car with a newer 8 3/4 and do how you get around the drive shaft that bolts to the three speed trans and rear? I want to keep the orginal flat six and three speed manual. Thanks Ron

Any good driveshaft shop should be able to build something for you.
The ball and trunion is not the best in terms of boot replacement and servicing. If you can replace it with a slip joint, you would probably be better off. Discuss this with your driveshaft person.