
The $C_{D0}$ table in Torenbeek's book. The version I have was published in 1982, at the time the B737-200 had been in operation for 11 years. Plus the following high-subsonic jet aircraft:
- Airbus 300 since 1974
- B-707 since 1958, including the stretched B707-320 operational since 1959
- B-727 since 1964, including the 727-200 operational since 1967
- DC-8 since 1959, including stretched versions through the DC-8-63
- DC-9 since 1965, including stretched versions through the DC-9-50
- F28 since 1967, including stretched versions through to 1973.
- Many others, such as the B747, Ilyushin 62, L-1011, Caravelle, Comet, BAC 111 etc.
The $C_{D0}$ values in the table were based on all high subsonic jets in operation at the time. Note that the B737 shares the fuselage diameter with the B727 and B707 - length of the current B737Max at 43.8m is still a bit shorter than the B707 @ 46.6m, so is the wing span. The 4 narrow cross section engines of the 707, versus the dual engines with much wider cross sections of the Max.
Nothing in the configuration changes since 1982 strikes me as a probable cause of an increase in $C_{D0}$ to that of a twin engine piston aircraft.