Stop in for a cup of coffee

You have to at the minimum take out the seal retainer. Which in the small block is the rear main cap. I don’t see how you can get the old seal out and the new one in with out pulling that cap. Which means another torque cycle on the main bolts/studs. That said, it’s not that bad of a job outside the car, BUT I also can see why he’s not happy. Especially given the money involved.
You are correct about the cap, idk what I was thinking, besides the fact that the crank doesn't need to come out. Just need him to verify it's not a pan seal, and like I said, we will send whatever is needed. With shortblocks we obviously can't dyno them. So, I apologize, and it sucks. I messaged @Mopar Tim back as soon as I saw it.