Finally got my rear manifold in. Now I have a new front and a rear with two new solenoids and four rebuilt (thanks Tom McCloud). I posted earlier on the front. It was in awful shape but I was able to salvage two solenoids and got two more from the back.
I am posting a photo in case others come across this solenoid corrosion issue.
The gray area points to a solenoid can with the washer rusted solidly to it. If you come across this, you may be able to stick a screwdriver into the can and jam the solenoid a little to one side. This may give you enough surface to try and drive the nut out. I was able to do that on one. This one, however, ain't comin' out nohow.
The red arrow points to another problem. In this case the nut is rusted onto the stem. You can unscrew the stem from the brass base but there's no way to hold it so you can break that nut loose.
I like the new plastic solenoids much better than the old ones. The old ones are an invitation to rust.
jor
Note: Both front and rear were working fine. Who knows? Maybe they would have gone on for the duration!
I'm sorry, the after pic looks way too nice.