OK....so after lots more searching I found some dimensions that were posted for a JD QA "shrub bucket". I cut and pasted the dimensions below in case anyone else is building a gadget for a JD loader. I believe these are the same dimensions for a 300 loader.
This would be allot easier if my tractor was close-by or if I knew of another similar tractor to measure stuff. Anyway.....here are the dims:
Re: Shrub Bucket
--------------------------------------------------------------------------------
OK, here's what I measured:
Bottom pins center to center = 46.75"
Top brackets center to center = 40.25"
Bottom pin center line to highest point on underside of top bracket = 15"
I don't know what the official dimensions are for a 430/460 loader attachment, but these work for me. There is a wee bit of slop, especially in the top brackets, so these measurements are probably not exactly to spec, but they should work OK.
btw. I'm almost done my next project - just needs painting. Stay tuned to this forum for my home made rear blade ....