[Alex Smart]

Hi,
Here are the engine numbers for four B-29's.as given in the macr's.

Macr 7178 - 42-6256 " Ramp Tramp".
Engine type : R3350-23A.
A - 42-84650 ; B - 42-84554 ; C - 42-121242 ; D - 42-120792

Macr 7523 - 42-93829
Engine type : R3350-23AN
A- 42-83723 ; B - 42-84263 ; C- 42-84238 ; D - 42-84285

Macr 9664 - 42-6365 - " General H.H.Arnold Special"
Engine type: R3350-23A
A- 43-150191 ; B- 43-150438 ; C - W-461315 ; D - 42-120951

Macr 9865 - "Ding How" - 42-6358
Engine type: R-3350-23A
A- 43-150019 ; B - 43-150406 ; C - 43-149707 ; D - 43-150063

So your number must be a manufacturers part number.