OK a number of points
1, I am making the assumption that your 6 speed box is a Caterham article, if it is the 6 gear is not an overdrive, the box does not have one.
2, A manufacture quoted BHP figure is given with perfect conditions. That includes no alternator load, perfect intake air density and temperature etc etc. The reading is given from the Flywheel to remove losses, which occur through the transmission.
You will never have this perfect condition, because your engine is install in an engine bay. The clutch, gearbox, prop shaft, diff, drive shafts, wheel bearings, rear brakes are all taking a little of your power. So you always end up with a lower figure at the Wheels. There is something wrong is you don’t.
Rolling Road BHP figures will vary from day to day, Rolling Road to Rolling Road, and operator to operator. Rolling Roads should only be used to see if your vehicle is running under load correctly, so it’s a setup tool.
Did you gain a power advantage from your first Power Run to the Last? If you did your Rolling Road was worth the money. If you went to the Rollers just to get a BHP figure for the PUB you have wasted you money, you are always better of use the Caterham figures.
Anyway if you are looking for a PUB figure quote the Caterham 0-60 or the Caterham Power to Weight, and if anyone dares to question them, invite them to a track day
Hope This Helps
Chris
PS I think 132 BHP on the rollers is good figure for a quoted 140 BHP car.