Maybe you find this to be helpful and you can quite posting the same threads over and over again.
This thread contains a scan of a very early 80's Seymour Duncan catalog.
Please let this be a lesson to you, actually 2...
Lesson one...Using the search function can not only get you the answers you seek but it can also help prevent you from driving other forum members crazy.
Lesson two...There was NO EVH/78 pickup being marked by SD in the time frame you are talking about.
The pickups listed in this catalog are:
SINGLE COILS
STL1B-Broadcaster Lead
STR1-Vinateg Tele Rhythm
SLT1-Vinateg 54 Lead
STL3-Quater Pound Tele Lead
STR3-Quater Poound Tele Rhythm
STL2-Hot Tele Lead
STR2-Hot Tele Ryhthm
SSL1-Vintage Staggered Strat
SSL1L-Vinateg Staggered Strat Left Handed
SSL3-Hot Strat
SSL4-Quater Pound
SSL2-Vintage Flat
SSL6 Custom Flat
SSL5-Custom Staggered Strat
SSL5L-Custom Staggered Strat Left Handed
STL2T-Hot Tele Lead Tapped
STL3T-Quater Pound Tele Tapped
SSL3T-Hot Strat Tapped
SSL4T-Quater Pound Strat Tapped
HUMBUCKERS
SH1B-'59 Model Bridge
SH1N-'59 Model Neck
SH2N-Jazz Neck
SH2B-Jazz Bridge
SH3-The Mag
SH4-The JB Model
SH5-Duncan Custom
SH6-Duncan Distortion
SH7-Seymourizer II
Notice, NO Mention of a EVH or 78 pickup anywhere.
Also notice that the numbers go in order and this catalog is from the early 80 and they were already up to SH-7.
If you are looking at an early 80's catalog and there is NO mention of an EVH/78 pickup then there is NO WAY they were making and marketing it in the late 70's...if they were it would still be listed here or there would be a break in the numbering system.
Also, before you start with your conspiracy theories reguarding the 2 pickups oyu see listed that are not still mentioned in the Duncan Line up, the SH3 The Mag pickup was renamed Stag mag years ago and the SH7 Seymourizer II is now known as the Duncan Distortion Neck version.
Here is the catalog, look for yourself.
Since there is NO mention at all of an EVH/78 pickup, please consider the matter closed. Seymour did NOT market an EVH/78 pickup in the late 70's...it just didn't happen.
Check for yourself.
https://forum.seymourduncan.com/showthread.php?t=93141&highlight=vintage+duncan+catalog