I think it was truckernix that shared this link about engine ID a few years ago. I believe it shows your early 235 with the tall pushrod cover.
http://pugetsoundvintagechevrolet.org/Programs/6%20cylinder%20engines%20with%20photos.pdf
I do not know the answers to your other questions and would suggest that you will never get the best response from other members because you are burying questions about new topics under an old title about engine ID.
The ignition parts question should be a separate question under a new title.
The gear box question should probably be in the driveline forum under a new title.
Just be aware that the moderators frown on the same questions under different titles or in multiple forums so you could edit your last response above (click on the grey "edit" button in the lower right corner of your post) or expect some leniency from them in your first posts since you are a new member.
Hope this helps.

"Nothing astonishes men so much as common sense and plain dealing." - Ralph Waldo Emerson