Well C is harder to answer, the stock 1st over could be rebuilt again where the 90mm you would probably have to sleeve to rebore, but how many more times are you likely to rebuild an engine on a perfectly restored Tii, it's not going to get that many miles on in most cases. As to forged or cast I would prefer the cast piston for a street engine unless it was boosted or extremely hopped up and driven that way. Don't get me wrong forged piston have their uses, but they also have their own set of baggage. as for which Tii would be worth more, I don't know but I would like to see two perfect and consecutive numbers Tii's side by side.