Hello Red Kelly,
The engine number is located on the block (NOT the head) under the 5th and 6th spark plugs.
It should look something like 130983 12 XXXXXX where the Xs represent the number of the engine.
279 manual antenna
426 power steering and automatic transmission
Have a look at the "databases" list on the homepage of this site. You will find the options database from which you can determine your options and when you receive your data card and its explanation of the installed options, you will be able to compare them.
Also have a look at the Mercedes Veterans site
www.mercedes-veterans.com there is a link to a database that shows where a car was delivered and you can also work out the order number and the year of ordering too.
Bob (Brisbane,Australia)
RHD,1967 early 250 SL, auto