I hope you put a reasonable amount of silicon on the corner of the seal carrier where the oilpan meets the block. thats a huge leak spot. there is nothing wrong with tapping the seal in with a flat punch and a hammer, its big enough that is can take some flex.

One thing though maurie...I am worried that your G54B clutch isn't strong enough, you plan on pushing your truck hard with a clutch that is rated for less power than the original one.