383 oh what to do

I'd rework the 383. Things to factor are will your existing exhaust setup work with the taller deck RB? The intake is different too as is the distributor. If you don't have these they add up along with pistons, machine work, etc. If the pistons, bore and cam is ok, just redo the bottom end and add the Indy heads. Then if you want more build the 440 short block while you run the 383.

If money were no object then a stroked 440 would be the way to go. I guess it depends on how deep your pockets are and how fast do you want to go?