I have swapped my stock GM 151 For a fuel injected small block chevy, I retained the stock bell housing and hydralic clutch, but I have been going through a slave and master cylinder about once every 6 months. are these just to weak to hold the force of the bigger clutch plate or is there a more sturdy set up for a reasonable price, even if it includes swapping trannys.advice please?  

If it's just the clutch master and slave that are giving you problems you should be able to swap larger units from say the vehicle you got the engine from. Just a thought.