RE: Looking for Cox .049 mods?
Besides detailing the crank fit and opening up the airway, the most important mod of all is to thin the piston walls to paper thin and to raise the skirt to obtain .010" of SPI. The ball socket should have zero slop. Beyond that, going with a 128 tooth NVA is mandatory.
The easiest way for anybody who wants to see how to make a Cox .049 run would be to examine a KillerBee and do your best to copy what that engine has had done to it.