Blew it up... GRRRRR!!!!!

Make sure you're getting oil to the rockers on that cylinder.

With used parts it's POSSIBLE you got that one in 10 million chance of 2 going bad at once, but next to each other is astronomical, or by some faulty design.

I'm not convinced you have a fitment problem, coil bind or such other problem, but it could be a lube issue.
With the pushrod seats destroyed, you can't even tell if the lube holes were plugged, now.

Mark.