I use a 3' extension and sometimes a u-joint. Just depends on if I can get it wiggled on there or not. Size depends on if it's stock or with tip over bars. I don't know about Murphs, but Skip used SAE sized bolts for his mounts. It's not uncommon for previous owners to have replaced the OE screws with SAE bolts either.
Make sure they're properly shimmed too. If there's too much gap the engine hangs on the bolts and will eventually break 'em. If you try to torque until the gap is closed, the bolt will stretch, the engine will hang on the stretch bolt and... Just shove in the thinnest washers you can easily find that'll fit over the bolt until you can't any more. Then torque the bolt. The spec'd place to put the washers is in the front left (as sitting on the bike) mount. Torque the others first, then shim the F-L and torque it.