D45 mirror reinforcement arm/bracket

[K25alive]

Looking for feedback regarding these mirror supports. They are used to reinforce the lower mounting bolt on the D45 below-eyeline mirrors. I pulled these off two '88 Suburbans. Note the shorter/smaller one came off the driver door. Are these supposed to be two different sizes?
I'm going to remove the camper mirrors and add the D45 mirrors to my '79 K25 truck. So another thing, how would one know precisely where to mount the mirrors on the door so the reinforcement arm will line up? Is there a diagram available out there?

[mongocanfly]

Mine do not have that brace..but my mirrors are 11" from leading edge of door to center of mirror and 1" below window rubber to top of mirror frame cover.

[K25alive]

Thanks for the input mongocanfly. Anyone else have experience with installing these mirror brackets? The GM p/n is 14007541 & 14007542 or interchange with 15628627 & 15628628. I thought I've seen a template before that lays on the door in the correct orientation so holes can be drilled in correct location.

[oldgold70c10]

Reviving a dead thread here, but I am currently in the process of replacing the standard car-size mirrors on my '83 with the D45's.
The outside mirror bracket which goes on the doors is the same L & R. The bottom mounting hole is off-center. Hence the reason for the passenger side support which goes inside the door being longer.

As for the mounting location of the mirrors, I think I found out how to determine this relatively easy.
Inside the door under the vent window is a reinforcing plate where the standard mirror mounts. This plate has a hole in it with no hole n the door skin. Drill a hole thru the door skin where the hole in the backing plate is and this establishes the front top mounting hole for the D45 mirror bracket. Drill this first hole and then mount the bracket and get the top edge parallel with the window sill and drill the other two.
The hole in the inside door skin is already present for the support reinforcement.

I hope this info helps because there is very little info about this online.