well shoot, that does sound painful. in retrospect, i bought the whole kit from crutchfield for the head units i replaced, and they came with wiring harness adapters, but i recall still having to buy wire connectors etc.
and the one car i did replace speakers on, i took my good old time and had to cut out bigger speaker wholes (it was an old olds, so i didn’t mind cutting it up a bit)
All that to say, hearing you recount all of that, reminds me that it wasn’t as easy as i misremember it being.