mpg for several vintage benz

[dpl]

Hi forum friends,
Can some body please me answer these questions?
1. What is the miles per gallon (mpg) for each one of these Benz models
A. 1980 350SEL, W116.028, ENGINE: 3.5L M116 V8?
B. 1980 280S, W116.020, ENGINE: 2.8L STRIGHT 6 CARBURETOR?
C. 1982 280S, W126.021, ENGINE: M110,924 2.8L STRIGHT 6 CARBURETOR?

PART 2 QUESTION:
I HAVE A 1968 280S MANUAL TRANSMISSION, CHASSIS: W108, ENGINE: M130. 016 0101 STRIGHT-6 2.8L, DUAL ZENITH CARBURETOR. I AM JUST AT THE POINT OF STARTING TO TAKE THE ENGINE & TRANSMISSION APART FOR REBUILDING IF DO DISCOVER THAT THE ENGINE BLOCK HEAD IS CRACK I WILL HAVE TO CHANGE THE ENGINE & TANNY(IF POSSIBLE) TO A 1980 OR 1982 BENZ STRIGHT-6 GAS ENGINE OR STRIGHT-8 BENZ GAS ENGINE & TANNY. WILL LIKE TO STICK TO MY MANUAL TANNY IF POSSIBLE BUT NOT A MOST.
A. WILL A 1980 350SE, W116,028, 3.5LITER M116 STRIGHT 8 ENGINE + TANNY FIT IN MINE?
B. WILL A 1980 280S WITH MANUAL TRANS., W116.020, 2.8L STRIGHT-6 FIT?
C. WILL A 1982 280S MANUAL OR AUTOMATIC TRANS, W126.021, M110.924 STRIGHT-6 2,8L CARBURETOR ENGINE FIT?
D. OR WILL A 1982 380SEL, W126.03, ENGINE: M116.963, 3.8L STRIGHT-8 FIT?
CAN THEY FIT WITH LITTLE OR VERY MINOR ADJUSTMENTS?
THANKS IN ADVANCE
DPL