How about this, compiled by PCA with help from PCNA & Porsche.....
Click to view attachmentAFAIK - & as Andy said, all the 76 MY's were actually built in late 75 in an effort to close out the 914 model, because the Karmann plant was switching over to the 924 production & had extensive retooling to do. They were also trying to use up their parts stock with the last of the 76 914s, as they had the 912E also available for the entry level Porsche - to fill in until the 77 924s were available for market.
BTW - for most car mfgrs. the model year starts in August/Sept. of the calendar year prior to the model year, and usually ends in the July/August of the same calendar year of the model year (similar to the typical school term for K-12 & college overlapping 2 calendar years). There was usually a 2-4+ week break between MYs' production, in order to change over the lines to the new upcoming MY.
This would've been the case at the Karmann plant preceding the 70 MY production kick-off in summer 69, and so on every summer thereafter - although there were only moderate body shell changes 70-74 to 75-76 MYs due to the 5 mph bumpers & their impact absorbing shocks, with the other MY changes being more akin to parts bin changes.
Not sure if this gets to what you're looking for, but hope it helps.