BigRed,
If the 305 is a late model roller motor, it will make a good stroker motor because of cam selection (roller cams) and should be able to produce at least 400 hp. If you want more hp, then the 350 is the way to go. You can use the same crank, rods, flywheel and balancer in either motor (rear seal is the difference, one piece or rope type seal), the pistons are different size.
Just a thought
Jim