3 bearing engine center shells needed

[Jeff Blight]

Hi we are trying to get a set of +20 shells for a 3 bearing engine with no sucess with the usal suppliers and we are reluctant to grind crank down to +30 as its good!ive been told its the same shells in the reliant engine can anyone confirm this,also is it possible to machine down a set of +30 to fit im not sure how much white metal is on the shell I would presume the steel backing is the same for all sizes so might be possible.
thanks Jeff Blight North devon 07891 036231