At .40 over I think you would be well into the water jackets....
Besides, I dont think boring .040 really hurts rev capacity. Its not like you are adding a significant amount of material to the piston to weigh it down.
Stroking is what kills rev ability, as the piston in a stroker motor has to travel faster than it would with a shorter stroke. The reciprocating parts can only accelerate and decelerate so fast.
One thing to consider before you put this in is a dipstick. 289s are meant to have the sump in the front, and I dont even think they have a blank where the boss goes for a rear/dual sump pan.

Are you getting this motor for a steal? They are cool motors, but I dont see the big advantage, especially if you are wanting to convert it over to a roller. You're also going to need a matching flywheel and balancer, since the old engines have the 28oz inbalance while the later(post 81 or something) has 50oz. Maybe I got it backwards, but they are different.

Thats all I can think of for now..