Big block and A/C?

Any big block owners with A/C out there? In particular those that are installing units on non-factory AC cars. If so what system did you use and what other options are you running? I'm thinking of buying an aftermarket unit and wanted to know what others are using. Are there any clearance issues with the right valve cover running the lines through the existing heater blower motor opening in the firewall? Do other options like power steering interfere with installation or operation? Thanks for any and all input.