I am going to word this as tastefully and neutrally as I can here, and if you would like a 3rd opinion i would gladly ask you to ask for one. But here is the story, and here is the source of the confusion.
For a 78 EVINRUDE 70hp the model # XXXXX XXXXX
For a 78 JOHNSHON 70hp the model # XXXXX XXXXX
They are the same exact engine, identicle in every way. The only difference in the market they were sold in in 1978.
The factory service manual is the same for both engines.
Part of this is my fault and I will accept some blame. My dealer software defaults to Johnson, and not evinrude, and I did not switch the tab over.
Both Johnson and Evinrude do not list a seal kit for this engine anymore.
If you want a seal kit from either Evinrude or Johnson (it won't matter), you have to order it seal by seal, gasket by gasket.
The part number listed above for the seal kit, 396349, is actually incorrect. There is a 0 in there. And it would be(NNN) NNN-NNNN But that is a moot point, because that part number has been discontinued a long long time ago. It is no longer available. It has not been superceded to any other part number.(at least that is what my software tells me, is that it is an obsolete part number).
If you want the factory seals from Johnson Envinrude, which was OMC, which is now BRP (confusing I know!) you have to order them seal by seal, no kits.
And this is going to get more confusing. the(NNN) NNN-NNNNnumber was a number that was carried by both Johnson and Evinrude, which at the time was owned by parent comapny called OMC. When OMC went out of business, and was purchased by BRP, BRP decided to not carry that seal kit any more. There is no Johnson, or Evinrude, or OMC as we know it anymore. There is only BRP. BRP still sells engines under the Evinrude name, but they are not the same engines. BRP decides what part numbers to keep, and which ones to get rid of, and that seal kit is one they got rid of. By all means please call a BRP dealer and ask them for the part number.
Now that other number above, 18-2660. That is not a Johnson Evinrude OMC BRP factory part. That is some aftermarket made in china companies part. I do not deal with that kind of stuff.
A good example is this, I have a Toyota Tundra. If you had a Tundra as well and asked me for the part number of the brake pads. I'm going to give you the Toyota part number. If there was not a part number available from Toyota, i'm not going to go get autozones, partsamerica, pepboys ect part numbers for all of the parts they claim to carry that may or may not actually fit and work.
I do aplogize if I was a source of confusion. These kinds of things happen when you deal with 30 year old engines made by companies that have been out of business for the last 15 years. But I do hope this settles some of that confusion.
And again I do apologize for getting Johnson and Evinrude backwards, but the rest of my answer was sound advice, and I do stand by it.
Post back with any questions.