I agree with you on Solidworks. I've got thousands of hours with Solidworks and a few other CAD software. For overall user interface and speed, SW is one of my favorites. I do all of my at-home and freelance design work using SW.
I'm curious about your FEA and flow approach. Did you model the head, or just put the piston in a cylinder and have a cap with similar geometry to the head with an inlet and outlet where the valves are?
I've had a few ideas about engine assembly FEA, but haven't had any time to actually try anything out.