1977 78 wiper wiring

[3x2GTO]

I have a 77 K10 that's had a 78 2wd cab installed sometime in it's past, but I think the wiring is the original to 77, because I believe it still has the 4wd LOCK light. I started a thread a few years ago about this, but took a break from working on my truck, now I'm back on it, so started a new thread, maybe someone can help me figure out this mess. Here's what I have: 1977 k10 short bed stepside, the VIN plate is affixed to the 78 2wd cab door jamb, they used hardware store rivets for this, but I'll fix that later. The glove box decal matches all of the equipment on the truck. The title, VIN and decal all jive. I know it has a cab from a 2wd, because I'm installing the correct 4x4 hump. I've looked at every inch of the wiring, even retaped a lot of it, there are no cut wires and it all comes back as a 1978. It's pinned as a 78, and the wiper plug is the 1978 on up style. At one time it had an aftermarket under dash mechanical oil gauge, I took it out because the dark blue oil sender wire is still in the factory harness, so I'm going back to the electric gauge. The gauge cluster housing and printed circuit are for a 1978 with gauges and no tach or clock, so I'm good there. Here's my main question. Right now the truck has the 1978 on up wiper switch, but has the old style 1977 and earlier wiper motor, but only works on 1 speed. I didn't know this was even possible. Is the switch the reason I have 1 speed, or are the switch and wiper motor not compatible? Someone suggested it was a late build 77 and had some 78 features, I don't know, but need to get my wipers working on high speed. Any suggestions? Thanks![ATTACH]



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