Rv 440 + 6-71 ?!?
I was thinking 5-8psi tops.
You are good to go!
What camshaft are you planning to run?
Stock cams work real well with boost as they have a wide LSA(112 to 114)
How many crank driven accessories are you planning on running?
If you arent going with too many acc or engine RPMs than run the stock single crank keyway.
If you plan on running Pow Steering, water pump, and mech fan, with excessive RPMs than you will want to have another keyway cut into your crank.
And always use a harmonic balancer, dont use a crank hub.