Steve,
The two best glass hulls are the Phil Thomas Stealth and Insane FE30.
The PT Stealth is epoxy glass versus the Insane FE being gelcoat and polyester. The Stealth does take a fair bit of pin hole filling and prep for paint, but I believe is a better hull.
To achieve 50 mph, I would recommend the following for a power system:
Motors:
TP 4060 1950kv or a TP4050 2100/2350kv motor
Castle 1515 1Y
ESC:
Swordfish X+220A or OSE Raider 150A if you use the TP4050 2100
Batteries: 45-80C, 4S2P 8000-10000mAh total. Many options here to choose from.
Props:
Octura X440/3, X447, X450, ABC 1716, 1814, 1914
That will get you 50mph pretty easy with low stress on the power system.