External pump for wet sump question

[sparx]

I was talking to a guy who has made up a mains cradle for his inline 6 and has in the process has made redundant the mounting for the internal pump.The pump is cam driven normaly and has a pressure relief valve to keep pressure under 60psi.He wants to run turbo's and therefore will require some additional flow.Anyone know what sort of GPH flow he would need in a pump and what sort of pressure relief system is used on this type of set up?
Thanx Sparx.