It's not difficult to remove both engines and outdrives, fill in transom and glass in new engine bearers in the centre. Refit engine and drive and you have a spare unit. My friend done this on his boat over 3 weekends. To convert to shaft drive is not practical as you would have to move engines forward quite a distance to get the shaft angle correct, you could turn the engines round and fit v drive gearboxes but this would be expensive with the cost of gearbox, shafts, bellhousing etc. To change to single outdrive it mainly fibreglassing, if you can't do it yourself you can do the donkey work like getting the engines out and getting hull ready for the conversion. Good luck. Jim