Hi Marty,
Sorry, I've posted all the relevant info I could find. I've just had a look but can't see a patent, so there probably wasn't one. Here's detail from the drawing I posted earlier in this thread.
I see two ways forward.
1. Just fabricate a "bridge" to hold your gearbox. Draw out a plate for either side, parallel through the centre, with an ear at each end to go down to your bolt holes. Cut it out of cardboard to make sure it is going to fit, then gut it out of 1/4" mild steel plate. (These days get it cut by laser/water/whatever - probably cheaper and quicker.) Get another piece of steel the width of the frame lugs, maybe 3/4" thick, and appropriate length. On the underside, mill out a slot to match the ridge on top of the gearbox, and two slots to suit the studs. Weld or bolt your plates on either side. Bingo.
2. Beg or borrow or make a pattern for the correct piece and have it cast. It's easy if you have the right friends, difficult otherwise!
Good luck,
Leon