anyone use a comp roller cam and lifters in LA small block

I have tried to get info on the roller lifters from Comp Cams and they have not sent or told me anything.

My ? is What mods have to be done to the block to install roller lifters in a 1971 340 block?

I have been told they have some direct replacement lifters for this from a friend. I have heard the lifter bores would need to be bushed to install them form others

Does anyone here have any experience in installing them in an older small block not designed for roller lifters?