Camshaft & Valvetrain...
One of the earliest internal changes to the 430, other than the distributor which was re-curved around or just prior to 11-1-57, appears to be the camshaft. The 1958 service manual references the EDJ-6250-A cam as being used from 9-10-57 through 11-10-57.
I have no reference for what, if anything, was used prior to 9-10-57. Based on the old ads at the following link, the cars (Lincoln) were formally introduced to the public on 11-1-1957 http://www.plan59.com/tearsheets/news_index.htm
so it would seem that engine production might have only started in September 1957.
Early valve springs are brown or maroon colored.
Here are the early 1958 cam specs. First, from the Mercury Advance Service Manual for 1958:
The red highlights indicate possible typos or revisions based on subsequent publications (refer to 1958 RM specs guide posted later).
And from the 1958 AMA Specs pages for Lincoln9-10-57 through 11-10-57Intake duration= 276 degrees
Exhaust duration = 276 degrees
Overlap = 54 degrees
Later style cam and valve spring usage from 11-11-57 onward:
Later valve springs are green or olive colored.
Bulletin on the cam and valve spring changeover