Ah this nightmare. Yeah I had this too after using a nut of the wrong pitch and I couldn't think of a way to solve it either, short of pulling the engine out and welding a bolt in through that tiny gap the way John202020 suggested. I know some later models have bolts there rather than studs, not sure if there is an easier way to convert them.
In my case fortunately I was able to recover the studs with a die nut.