I have removed all case fasteners (20 smaller nuts and/or bolts plus 6 large bolts)--and I have checked at least a dozen times--and compared to various guides. At this point only sealant should be holding the case halves together.

But my gentle and careful efforts have not budged things. And even some slightly more aggressive tapping with a hammer and hardwood dowel has not worked.

What to try next? Any good methods besides the tool that wedges the oil strainer hole open?

Yes on the tool that inserts into the oil pump cavity.

There's one nut on the lower front of the case that's easy to miss. I'm with Bruce on the oil pump bore splitter. You can gently use a brass drift on the studs. Just don't pry it apart, you'll create an oil leak.

Try Jake Raby's method...make sure the front main seal and fan hub are still on the engine, then use a prybar between them, making sure that the edge of the bar is definitely pressing on the seal (not the case). If all your bolts are out, the case will split really easy this way....

Also make sure all the washers are off, they catch on the threads.

If its fighting you, either the case is being held up by a locating dowel pin, or you’ve left a fastener behind.. My engine rebuild video is a real life saver, here. I show each fastener.

1000%

Hope you're well, Jake!

Thanks, everyone. Cuddy (and Jake) are the winners. I did some gentle prying on the input shaft seal, and the seam opened along the front the middle. But the rear seam by the flywheel was not cooperating. I resorted to some plastic wedges (door shims) and that did the trick.

Thats how I did it yesterday.. worked like a charm against the seal..