You should be able to swap out the regulator/brush set with a new one. Aftermarket reg./brush set's should run 15 to 20 bucks, and the Bosch 2 to 3 times as much.

As far as the ECU goes, an '83 should be a "503" with a single wire o2 sensor. The '84 should be a "510" with a 3 wire o2 sensor. If your car is wired for a 3 wire o2 sensor, keep the "510" in it. Your other option is to switch the o2 sensor, mass air flow meter, and ECU from the '83 to the '84.
Either year car could have a "California emissions" set up, and be wired for the heated three wire o2. Don't swap anything if the thought of the smog police will make you loose sleep.

The 83 and 94 B23s have identical AMMs and the ECUs are fully interchangeable. The numbers might be 503 vs 510 but they are equivalent. Do not discount the possibility that the ECU is the problem as this is a known and common failure in B23s.

In short answer to your first question: yes.

Long answer: Pretty much any alternator from an OHC red block will work. They're all almost identical, and quite durable. In fact I'd bet that the alternator on your car that "died" doesn't need to be replaced, rather it needs a new regulator and/or brushes.

If you pull one from a 240 you will have to watch out for the connectors on the back. The OE alternator on my brick had a spade terminal for the thin red wire, the one that I replaced it with (Bosch reman from a junkyard 86 240) had a normal lug thingy. Similarly the replacement had slightly smaller pulleys. Not enough difference to warrant different size belts.

If you had pulled one from a 740 you may have to worry about the pulley (2 belts for the 240s, the 700s had one alternator belt).

Some of the later alternators fitted to the 700s were rated around 90 or 100 amps, a nice improvement... but you may have trouble fitting it if space is tight on the exhaust side like it is on a turbo.

2nd question: AFAIK no. The 83 and 84 had model year specific AMMs and ECUs I believe. If you swap both they should work.

- alex

'85 244 Turbo