A 350 in a 16 footer is a bit much, but... for gearing something in the 1.51:1 or 1.4:1 range, and props in the 21 - 23 range will be close.
My vortec 350 VP on an 18 1/2 ft has 1.51:1 gears and swings a 20in Raker or a 20 in Enertia at around 4900 rpm.
I did assume your 350 is a marine engine. If it is a car/truck engine, it will be next to impossible to get propped for proper WOT and still have good holeshot. If it is a car/truck engine, you will need USCG certified Carb, Flame Arrestor, Distributor, Alternator, and Starter. You might be able to reuse the Alt from the 250