Help deciding what set of props I need
 

So I have a 24’ pursuit with a Volvo penta DP-C stern drive. I bought the boat with no motor and over the winter I installed a 383 with a aftermarket efi kit on it. I’m assuming it’s making close to 350hp. I’ve put about 10 hours on the boat so far this summer and it’s running flawlessly except for the fact that it will just barely hit 30 mph at about 5500 rpm (wot).
The boat currently has a set of C4 stainless steel propellers. What I’m trying to figure out is, should I bump all the way up to a C7 set or go with something like the C6? The gear ratio on the drive is 1.95:1. Pursuits website also claims the boat could do just about 50 with the 5.7 (roughly 290hp)