Yes, a manual 123 regulator will fit the spot where a power regulator was located. I'm not so sure about the sedan to wagon swap... but with most 123's it's plug and play. This is a simple fix. Non power windows on the rear doors were an original "option".

You will also find that new manual regulators are "cheap" when compared with power regulators. On my 300D my rear regulators were bent by the power motor so that the gear was jammed and bent. Lucky for me the windows were in the up position. When we checked out the price of the regulators here is what we found: $450 - $500 each for a power regulator; $65 each for a manual one. The handles were about $5 - $10 each. The male shaft that fits the handle goes through the rectangular hole where the window switch is located on the rear door. I made up a vinyl circle with a small board inside the vinyl to cover the opening. I'm going to search for a proper used door panel later.

Make sure you remove the wires from the block of the old power window system and use some shrink tubing to cover the individual pins so you don't get a short (and start a fire). Then wrap all of the bundle in tape or a large shrink tube and push it back through the door to B post tube to ensure it doesn't get caught in the window mechanism.

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Pete Williams, President emeritus - MBCA-International Stars (Eastern Mich.) Now Wi. & Az.
1985 300D Manual 4 speed Green Hen's tooth
1979 MGB triple black Az car nice
1969 back 1/2 of MGB (Az home built trailer)
1991 Volvo 245 Wagon Nice AZ Restored Gold Brick
1983 Jeep CJ7 37,600 Miles Summer use only