Beat me to it. Throwing a stock 351W into a Mustang is like polishing a turd. That motor your friend has is only worth that $600 for someone just swapping out a burned up motor, but not in the performance world. You would want to strip that block down, get it machined, get the rotating assembly cut and/or polished if needed, then balanced if not going the stroker route, new pistons, heads, cam, intake, blah, blah. You'd be better off with the stock 302 already in the car. As mentioned the stock 351 is heavy and not to forget they have low comp dished cast (weak) pistons in them. The heads are the exact same casting in the Mustangs only that the head bolt holes are drilled ½ inch which is required for 351Ws and are a major restriction. Cam selection would be a lot better if the block is from a '94-newer truck/van (F4TE). Those are roller-cam ready blocks. The stock induction parts for the van would make excellent additions to coral reef restoration projects.