So look at the better pics I added to the above post. The trusses are actually added on top of the side bearing caps and longer bolts are used. If I could find an old T100 diff from a junkyard, I'd be willing to bet those trusses would bolt up to my carrier. Then its just a matter of seeing if it will fit inside my axle. And if not, then I just need to blow out the back of the diff and add some steel to clearance the trusses.
Ok Rick, kinda following but not exactly so sorry if I'm way off. But I think you are trying to fit something inside the pumpkin to help support something else and you need to determine clearance. But of course since you can't get a measurement tool in there you have to come up with another way...so here is what I came up with...first cover any parts with cellophane, both the inside of the diff cover and the ring and pinion, then attach the cover, open the fill plug and use low expanding foam and fill the cavity, once the foam has hardened you can remove the cover and out comes the "air space" inside, which you then can take measurements off of to see if your device will bolt up and fit....and there may be other options like a Teflon spray coating or something other than cellophane.