Greetings! I'm in Cali as well, just under 6'4" and 235, I have a 49cc Huasheng. It has adequate power for me, but I typically cruise 20-29. My bike's top speed on the flats is 34-36MPH, it wouldn't be able to hold that speed with any headwind tho. It's not so much the weight as it is the aerodynamics that hold me back.
A GXH50 and a Q-matic might get you a cruising speed of 35, but again, probably not with any headwind. You'll either have to drop your expectations to a 30MPH cruise or use a more powerful engine, like a Predator 99cc.