Bigger brakes for MGB

[drake@direct.ca (len drake)]

I have a 1970 MGB Rdstr running a Rover 3.5L V8 that is used on the street as
well as auto-x-ing.  Does anyone know if bigger brake rotors off of something
else can be adapted to fit the MGB?  I know that Moss Motors is selling a 
Brake kit that uses bigger vented rotors, but they are quite expensive.
Does anybody know what the original OEM application is for the roters in the 
kit from Moss?  Thanx in advance for your help!
-Len Drake