I'm not familiar with the big block in your truck , but obviously you need to get the sump off , remove the rear cap , and get a long punch , keep away from the crank surface and tap the seal around , you'll only get so far , then you'll need to get a hold of it with some pliers and drag it out , it's easier if you can loosen the other caps a little and move crank down a tad , but you have the trans on , they say the cometic viton seals are the best , watch out on the install you can shave the seal on the sharp edge , maybe a careful file on the edge , leave seal ¼ up and set cap seal the same opposite side , I just use oil on it , I've seen the moly stuff dry out , not good , also on some instructions I had once said no sealant on the ends , which I think is a good idea because if you put some silicon or something on the ends and it squeezes out then it interrupts the seal edge . Cheers mate .