Last winter I did exactly this job on my '69 144S. In my case I substituted the rear from a '73 w/od (4.30 gears instead of my 4.10) and added limited slip saved from a '76 265. Your estimate for parts is a valid estimate--especially if you have the early style 140 rear (handbrake enters at the top of the backing plate). Those rears use different (read more expensive) seals and bearings than the later type (handbrake at bottom) which share internals with the entire production of 240's. You can get a seals-bearing-locking ring kit for about $55 each side for the later type. The carrier bearings ran me about $70 for the pair from a local bearing supplier. I left the pinion shaft/bearing/seal alone and reused the ring gear--A friend rebuilt his 240 with new gears at about $175 for the ring/pinion set. I'd look for a serviceable later style 140 rear and just install it--if it ever needs rebuilding the parts are less money and easier to find. The early style handbrake cable (longer than the later type) will work on the later rear. I don't think the later cable will stretch to fit an earlier rear. If you were closer you could come and pick up my functioning original rear which only needs seals (of course, that means pressing off the lock rings and bearings)---cheap. -- Dave