Mercedes had cast heads on the 4 and 5 cyls till the later 80's.. I think the Toyota also had a cast head.. Isuzu typically has a cast head as well.. I dunno about the Mazdas used in the early Rangers.. I think the later Rangers had an aluminum headed Perkins TD.Bang for the buck may be to yank one from a rusty Benz.. they can be had pretty cheap..
I was referring to the GM 350 diesel.. C'mon, you know you want to be a glutton for punishment, let's see how much boost one'll take!!!