V8 in slant 6 k member. What am I doing wrong

OP, your stuff is fine. The /6 pedestal on the driver's side of your k frame is the same as on a smallblock k. Using a smallblock bracket and mount on the driver's side locates the engine in the factory location. The passenger side bracket should just level things out, and does not change the location of the engine. The truck mount just happens to fit the bill perfectly. And it's all factory parts, just a different initial application. So no need to worry about replacement parts down the road.
I think your pic may be a little deceiving, and the pan is a bit closer than it appears- I have done a number of these exactly this way and others with various conversion mounts (Schumacher and Trans-Dapt), in addition to factory versions. Placement was always right where the factory versions are. If you look at the former Schumacher conversion mounts, the pass side is patterned after the Mopar truck bracket.
I have two different factory smallblocks in my shop right now- a '68 and a '75; both of them locate the pan 3+" off the k frame; and that's with old mounts on them- so you look to be right in the ballpark.
Time to tune out the noise and move on.