ashcroft transmissions have a bespoke ecu for the p38 auto 4speed box it allows you to tailor your box to suit any engine torque and bhp curves , but its £750 +the chancelors cut . you will lose sports mode on the box but hey you lose that as soon as you fit a diesel any way . and no i didnt...

H i , you dont say wether your motor is auto or manual ? , i had a good look at a gm 6.2 in a p38 manual last night and it fits well . some small fabrication work on the oil sump to slot it in . No auto box ecu electrics to fettle . im about to embark on fitting a 6.2 gm diesel into my p38 auto...

How Do Folks , A Few Familiar Busses From My Neck Of The Woods So I Thought I Might As Well Join In On The Fun.