flwheel question

I was recently just about given a truck equipped with a supposedly rebuilt or low mileage 440 that was originally installed in an RV.

I am considering installing it in my 1986 W100 truck that currently has a /6 N.P 435 setup.

Im assuming that I need to find a B.B bellhousing to mate the 435 to the B.B but I have been told that my new ( just recently installed ) flywheel/clutch/pressure plate assy ( which is 11 inch ) can be used on the 440 since /6 flywheels are neutral balance.

Can anyone either confirm this or tell me if there is any chance that this could be made to work. Maybe worst case filling and redrilling flywheel if there is such a thing.

I am guessing that I am also going to have to have the back of the crank machined for the trans shaft since I am assuming the 440 was originally mated to an automatic ( as it is now ) and again I want to use my manual trans.

Ive been told chances are the 440 is an externally balanced engine cause of year and original placement ( R.V )