1967 C10 with TH400 ???

[Lost in the 60's]

I picked this up last March as a weathered field truck and haven't really looked it over closely. I am starting to buy parts to get it on the road this summer and knew something with the column indicator was broken. I was told it was originally a 6 cylinder Power Glide truck.
Unfortunately, someone broke the left door glass to STEAL the friggen glove box door, the ONLY thing missing from the interior. So nothing to know how it was built.
All the engine mounts were missing too, so I procured them to install a high performance 292 I had built with a TH350 trans.
So today I was in the unheated back shed for another reason and thought to look at the indicator. When I wiped untold years of dust off of it, I was stopped in my tracks to see it had L1 L2 D on it ???
I know it could have been changed over the years, but would a TH400 have been used behind a 292 ??? I didn't get the driveshaft either, so nothing there to indicate a 400 input yoke. This truck is about as original as any I've seen/owned and I've had a bunch over the years, so I think this is the original indicator.
Oh, yeah, the part that I need is the head that is screwed onto the column cup that moves. In medium blue, please...

Now that I wrote all this, cobwebs are vibrating. I remember when I threw the 292/350 in to get them off the floor, the trans mount did not line up with the crossmember....hmmm. I THINK the member was too far back and I just "assumed" it was out of place from the removal process. Now I have to go back out and look at this closer...