Hello Glenn,
The 127.982 was used in the W111 220SE finback sedan from 1959 through 1965. they made over 66,000 of these sedans.
The other similar M127 engine was the M127.984 used in the W111 coupes and convertibles, but not very many of these (around 2,000).
Although the M127.981 of the 230SL is very similar in most aspects there are some major differences like (Cylinder bore diameter, cylinder head, injection pump, injectors, intake, valve cover, etc.) The most obvious difference is the two cylinder injection pump used in the 127.982 sedan engines. The block assembly and its major parts are the same as the SL except the sedans have the slightly smaller bore size as standard and no tachometer drive!
Joe Alexander
Blacklick, Ohio