Figured I'd copy this into its own thread, seems that can make it more useful for people searching for this information in the future. Please slap my hand if this is unacceptable here. :)
I took some pics tonight, and jotted down measurements and started marking up the photos with the measurements. I missed one... where the studs are located fore/aft, but as was pointed out - those measures should be the same as any of the other attachments that fit in that slot.
I think I got everything, if there's any question, let me know.
On the side view, with the weight slot inset and the locating slot depth, sorry for the odd measures- i measured those with my digital calipers, and figured I'd put what they said- I imagine rounding to the nearest 1/8" is probably plenty good enough though...
Hope it helps!
Kenny, OAL of the bracket is shown in the top pic as 13-1/4".
Also noticing this morning that I missed the inside channel width and/or the the narrow outside measure of the weight itself. Since I show the outside at 5-3/8", and we know the stock is 10 Ga, I reckon we're looking (fudging a bit here, since 10 Ga is a bit over 1/8") 5-1/8" inside bracket width, and the weight's got about 1/8" of clearance on either side to fit in, so the weight must be approx 4-7/8" or so. Don't take that for gospel, I haven't had much coffee yet this morning.
Was out in the shop and took another look at it, looks like the studs are 6-1/2" from the front (weight end) of the bracket on center - note, the measure I did for their placement skinny-side was not on center, it was to the edge of the stud.
Also, the inside dimension of the channel is 5-1/8" as I suspected, and the weight is closer to 4-15/16", so I guess I was close enough for gubmint work!