You are only going to fit a short engine in that space, that means a v6 or a 4 pot., There are lots of custom parts around to fit a commodore v6 in , which will give you power, cheap parts, and easy engineering. Or if you want to stay diesel, maybe an Isuzu light truck engine could be an alternative, but as with any conversion, you have to do the homework, research and most likely all the hard work, unless a kit has already been made for the engine you want to use. Its a LOT of work to do it yourself, and a LOT of money to pay someone else to do it for you.