Who is the best value for $$/quality for Yamaha RD motor work

[tonofun]

Any suggestions on a good quality RD guru that is affordable for bores/fitment, porting and head work for an RD 350 motor. There are a few out there, but i want to check into all of my options. Also, i have heard a few different opinions on expansion chambers for the 350 RD ....any thoughts??? Thanks