best way to install girdle

At you level, you don't need the girdle. If you really want to get an improvement in strength, install the billet main caps. That will make things pretty safe to about 600hp. Beyond that, just buy a better block. There's no reason for a girdle that ties poor caps together. There might be some good done if you have good caps tied together, but between fitting the caps, and fitting the girdle, it's not worth it to me.