Sam
When we make our welded diffs we do the following:
after fully cleaning the diff
weld the spider gears together,in the corners of each meeting of spider gears. then make two plates that would fit down in the open space on either side of the diff. weld the plates, one to each side of the open space on either side of the diff.
Viola! you have a welded spider gear differential. I have had one that has lasted 5 12hour and 3 24hour races with no problems. I have another made this way that is in a car that is now on its second logbook. I am sure this method will work for you.
dave parker
wdcr itc#97