Since few, if any of us on this side of the pond have ever seen a Ute, let alone worked on one, any advice you get from us will be an educated guess at best. The Chevy truck torque tube and universal joint system can be disassembled in the vehicle by sliding the pivot ball back on the torque tube after unbolting the clamp that holds the pivot ball to the back of the transmission and sliding the ball back on the torque tube snout. Then the transmission can be removed. Be sure there is no vehicle weight resting on the rear springs before disconnecting the U joint- - - -support the vehicle by the frame rails, not the rear axle tubes. The crankshaft rear main bearing seal can probably be changed without removing the transmission by simply removing the oil pan and loosening the main bearing bolts. The crankshaft only has to be lowered a few thousandths of an inch to change the oil seal, if you're lucky enough to get the upper seal loose and pull it out of the block. Getting the new one back in can be a challenge, and reducing the amount of leakage even with a new seal installed can be a crapshoot. My success rate on installing a rope seal in the vehicle has hovered somewhere in the 50% range over the past 60-something years. Good luck!
Jerry
