v8 to series2a gearbox

can anyone help i am fitting rover 3.5 v8 in my series 2a i have a problem getting the gearbox clutch to work i have all the conversion kit fitted bellhouse adp ,flywheel drilled converted clutch etc but the clutch trust bearing sleeve dose not reach the back cover plate by about 15/20mm
thanks

If i recall, the 2a box won't take the torque from a v8.
Or was it the other way round, a series 3 box wouldn't.. someone else will pipe up with better knowledge