Where can I find the plugs for making and OEM wiring harness for a 1967 Belvedere. I would need all of them . This would be for the head light harness and the one for the horns and horn relay. I don’t need the bulk head connectors. I all ready have them.

Year One and Classic Industries both sell the connectors separately but I don't know if they have all of the connectors you might need. Year One also sells the complete wiring harnesses made by M&H Electric Fabricators. You can't buy it from M&H direct as Year One has the exclusive distributorship for M&H for Mopars. I bought the complete wiring harnesses for the engine bay, dash, and interior for my 67 Coronet convertible. I just installed them and everything was there and they look original.

It depends on how accrurate of a connector you want.
I would say for the most accurate, find a harness being cut up from a parts car. And/OR try some of the part number searches with NOS places.
For the matching terminals I've salvaged originals - its a painstaking and time consuming task to open the crimps - but can be done. Success may not be 100%.
IIRC those are the silver plated terminals. The Parts Book is not always 100% clear on these things. The more you work with it, the more you can figure out. Exact match might turn up NOS with some patience

For lesser the 100%, the headlight connectors are a common pattern. Any number of aftermarket connectors will work. IIRC those take a 5/16" wide terminal.
The horn relay connector with two terminals is prob the same as on my A-body. Might be able to get away with a "packard 56" connector of the same configuration. No guarentees on that.
Probably better off using an original used, along with a new Chrysler type terminal.
Some examples of Chrysler type terminals, and sources in this post
https://board.moparts.org/ubbthread...m-h-door-jamb-connector.html#Post2778549

My experience with ad older M&H harness was they used some Packard 56 female terminals in places Chrysler did not. When the connections need replacing, I used a Chysler style terminal. That's when I discovered the Packard 56 Connector did not properly hold the Chrysler type terminal. Forunately I had save the original harness and was able to transfer the connector.