Spot on that Jezza, great description! Had a chat with the mechanic at my work today, he basically said the same thing. He is a bit of a landrover nut job, and he was saying at some point, when landrover was landrover, and not a box with a ford engine, that for some of the engines they built they used the same block for the Diesel engines as petrol engines. The only advantage he said of trying to do such a thing for a petrol engine, is that the bottom end and rods are a lot stronger in diesel blocks, so in theory could handle more abuse, I'd just have to swap the pistons as the diesel pistons arent concaved, which helps lower compression, as you pointed out Jezza. He said he's heard of such things being tried out in Motorsport (when he was a lad, many moons ago). He then went on to say that I could use a dizzy from an old Peugeot, insted of trying to drill out the block, as it fires from the camshaft. By the end on my dinner break, he was more into the idea than I was! But there's light at the end if the tunnel now! Going to search into this some more and see what I can dig up!!
