ok..... the stock 4.6 blocks have been known to go up over 1000hp with good internals, hell even the stock GT's will take 400rwhp all dayDepends if he has the feel for speed. 400rwhp would get old really fast to me. After that he is looking at a hell of alot of money to pull the motor out and forge that 4v. Somewhere around the $10,000 mark. After that the fuel system will cost a couple more thousand. Then the transmission will have to be upgraded. So on and so on.... And from the sounds of it I don't think he can afford the blower alone. Let alone what else would be needed after that...
you can buy built shortblocks thatll handle 800+hp for under 3K
an 03/04 cobra tank, dual SVT pumps and a KB boost-a-pump will handlt a ton of power
and anyways i dont think he is looking to build a race car, just looking for a newer/fun daily driver and weighing his options