Congrats, one of the truly great games.

The flipper mod is the same as was done to mine - Gottlieb flippers making the game a Frankenfirepower as I called mine.

The round tipped Gottlieb flippers, while head and shoulders above what Williams used at the time, are not precise enough for this game - great for target based stuff that Gottlieb did where precision shots weren't quite as important.

When you are ready to swap these back to Williams, you can get a fully built up and coil installed unit from www.pinballlife.com although they are on break at the moment. There's also the upgrade to later model WPC flipper parts that gives you the advantage of being able to replace the coil stop (the originals have a plate and coil stop single unit). Details here http://www.pinrepair.com/sys37/index3.htm#flip

Have fun!!