I am using one on my 57 392 works good but I think it makes a clicking noise, didn't check to see if it is coming from another problem though.
I know the one that I sell will fit a 392. The clicking noise is due to the actual (stock) mounting position difference between an early hemi pump and the 318 pump.
The thickness varies with the maker...some are ½ some ar 5/8. This is the basic problem with using the LA pump; where does it fit best. Take your stock pump and lay it on your work bench with the mounting flange against the edge. Mark the top and bottom of the flange and draw an outline around the pump arm and point an arrow at the center of the wear patch. Now, do the same with the LA pump and put a spacer of something behind the flange. Where is the sweet spot? .