Iam not a wvo/svo type guy so won`t add to that.
I personally like the W123 body 77 - 85. 77 to 81 they used the 617 5 cyl none turbo engine and from 82 to 85 the 617 turbo engine. they all were automatics.
The 77 thru 83 240D used a 616 4 cyl engine either automatic or a 4-spd manual trans. 77 to 79 had 62hp and the used the larger loop GP`s that were wired in series. one burned out, they were all none op.
80 - 83 the HP increased to 67, and the engines were up dated to the small pencil GP`s wired in paraell. 81 was the first yr with the EGR.
77 - 81 the 617 none turbo was 80HP
82 - 85 the 617 Turbo engine was upgraded to 123 HP.
240`s have the type one heat/ac system which is the manual system, and the 300D`s were the more complicated type 2 and type 3 automatic type.
the 616 & 617 engines are all cast iron engines. the W201 and the W124 diesels as well as the W126 diesels 86/87 & 90/91 had the aluminum heads and got more complicated as time went on. the experts can chime on these engines.
A 240D with a automatic trans can be slow on the get up and go compared to the 4-spd manual transmission. the 4-spd will do much better on milage.
On some steeper grades in the mountains, you will be down to 3rd gear and doing 40+ MPH.
There were no 5-spd manual trans offered in the North American market in the W123/W126 chassis.
If you live in Arizona, it would be best to stick with R-12 freon. 134a will work, but will not be as efficient unless you do some upgrade to the system.
R-12 is availabe if you look around, I did a check in the Phoenix CL and found one guy selling a 30lb jug for $375.95, that`s $12.50 a lb. I have seen it a little cheaper, but a better buy than picking up the 12-14oz cans for $20 - $60 ea and saw one guy selling a 134a for $100.
R-12 PURE VIRGIN (NOS) RACON 12 FREON 30LB JUG ALMOST FULL **DEAL**
this guy has a 25lb of Hot Shot a replacement for 12 and 134, for $175, thats $7.00lb. but once you add something that is not what the shops use, they don`t want to contaminate their equipment, then you have to do your own work.
Hot Shot Refrigerant
These are old cars, the oldest 35 yrs old and the newest 123 27 yrs young. they all will have to have somethings done to them to keep them going and to take care of prior neglect. there are beaters out there and nice examples, depends what level of car you are looking for. If you are a DIY type of guy great, but if not then you are at the mercy of the shops. bend over.
Charlie