Re: 69 1250 impellar job
I have done it both ways.
If you don't have power trim and want to tilt the engine to get the LU off: forward.
If you have the room under the engine as it sits upright to pull the LU out of the mid section: neutral.
Don't change either the LU or the shifter while you work on the water pump.
If you turn the drive shaft a bit, (try not to do that), turn the flywheel a little bit to get the LU back in the splines at the base of the crankshaft when ya put her back in.
Hope that helps. JR