grubee's are good engines, usually. i've built 6 bikes with them and i like 'em. haven't had the 2010 model yet, though.
the head can go on either way. there's no performance increase, it's basically designed for clearance.
the barrel can be reversed, but there's some work involved. check my thread on it here: http://motorbicycling.com/f38/backwa...son-13458.html
in america, it's a 66cc, in china, they measure funny, so it's an 80. check the Grubee website (ads on the left of the screen) and they explain it.
acme labs is working on a V twin. there's a thread here somewhere, just use the search.
not from texas, so couldn't tell you about the laws there.
i've never used an expansion chamber, but sick bike parts has one, and people seem to like them a lot.
welcome to the forum...