Transmission question

You want a 69 and later. 68 and earlier have a one pin nuetral safety switch which wont work with your wiring harness. The valve body in the trans is different so you cannot just swap out the switch.

You may have a 727 torqueflite but most likely have a 904 torqueflite. If you look at the trans pan, the 727 has kick out in the pan where the dipstick tube goes. 904 does not.

The 727 is much larger, longer and heavier. You should be able to find a 904 for reasonably cheap. Whatever you put in it, bear in mind that the bellhousing pattern that bolts to the engine is different for slant six, small block and big block.

Honestly you should be able to find someone in socal, even (or preferably a hobbyist) who can rebuild it for a reasonable price. If the trans has failed change the torque converter as well and flush the cooler.