Differences in 350 valves by year?

Does someone have a link to a site that describes the change to Buick 350 valves and springs by year?

Ive noticed kits on ebay mention they are good for 70-74. I assume my 76 is different, buy how so?

 

75 /76 they changed exhaust valves from 1.500 to 1.55 as emissions changed.

 

So springs and seals are the same?

 

Springs and seals should be the same.