The video that Brad put up isn't for the 4G54 (obviously) but it should be noted that, in that DSM graveyard 'tutorial' he uses a metal type freeze plug thing to seal off the upper balance shaft hole - this is really risky. They leave the cases open to cracking, leaking oil etc. Yes he does make a point of tapping it in gently and using an epoxy to glue it in (?) but if you use the right blanking seal it won't grief you at all.