dont bother with those mate, use a socket extension and look down it and use your eye to align it, that's how ive always done it and never had any problems
Only other tip is might be easier to take box and engine out complete and then attach gearbox to new engine and fit back in as one lump as its not much harder as long as you get the right angle when lowering it back in.
You will need a decent engine hoist. Lots of cups of tea and take your time mate.
Hope this helps you, if you was closer I would happily come and lend a hand