Now that I'm piecing this thing back together, one of those little details is broken locking tabs on a couple of the (3-pin spark plug) coil pack connectors.

None of my other engines use these things, they all have the coil pack on the manifold.

So I know which cars in the junkyard are likely to provide replacements, can anyone tell me when and where they started using these in the H4?

Don't bother with the junk yard. Those always break from heat and age.:

The H6 uses the same connectors as the WRX. Just call iWire and get a 6 pack. All you need is the housings - you can depin the wires and slip them into a replacement plastic housing. No splicing that way. 

https://iwireusa.com/products/black-and-white-coil-pack-plug-kit

GD

Shipping would be slow and/or prohibitively expensive... but... lookit that - they have a Calgary dealer.  I'll check with those guys.

don't some folks just ziptie those things together?

or used a 'blob' of silicone. should hold together OK, and easy to cut through 80K miles from now.

Some folks vote for... no, better not.

Okay as a battlefield fix, but otherwise not my style.  Call me anal-retentive, but I like cleaning up loose ends properly.

We stock them for the same reason. Comebacks due to random misfires from poorly connected coil packs are common. We replace the housings anytime we find broken ones and the customer gets charged $15 per. Just the nature of these. 

GD