I'm happy to report that my new pushrod gasket is drip tight! No more oil leaks!
Getting the old gasket off was a royal pain in the keaster, but I'm glad I bit the bullet. I installed a new cork gasket using a cement sealer called Gasgacinch. This product was recommended to me by a couple of old mechanics I know. I also straightened the cover as described above, which may have been the problem. It turns out the vent tube was not leaking after all. It appeared to be leaking, but the real source of the leak was the pushrod cover located behind the vent tube.
The first gasket I installed was the pressed paper variety, and I cemented it in place with a product called "Super Weatherstrip and Gasket Adhesive" by 3M. I'm not suggesting this is a bad product, but the gasket leaked in several spots even though I know I installed it with care. Perhaps I over-torqued the original fasteners, but I started at 6.5 ft-lbs, just like the book says, and worked my way up to 10 ft-lbs.
