Unless you want to get some porting done, send it directly to US Chrome http://www.uschrome.com That's where Eric sends all his stuff. You'll either need to send a piston with it or they may be able to get one for you. Call them. In anycase I bet you can get it done for less than $387
How does the pricing work on the Big Bore kits? I looked on his web site and it says "1993-2003 KX310 $325 (Labor & Gaskets only)" and for the 265cc big bore kit it says "1982-2003 KX250 (265cc) $400" im confused on the 310 kit what does labor & gaskets only mean and why is the bigger kit cheaper?
The piston for the 310 kit is one that Eric designed while he was working as Technical Director at MaxPower. They cut an exclusive deal with Wiseco so the only way to get that piston is to buy it directly from MaxPower. As a result the 310 kit price is shown without the piston kit.
I just found out that MaxPower charges $200 for that piston. (Their cost on the piston kit is less than $80 :| ) Unfortunately they are the only source so they get to set the price.
The 265 kit will give you most of the performance of the 310 kit and no one will gouge you on the parts prices.
I'm not sure whjat the percentages are but lots of Vet MXers prefer a big 250 to some of the other chocies. As a play bike or enduro mount it's a nice balance.