OK....here's the final result. Got them welded in, welds ground, and topcoated with Zero Rust. I'm very happy with the result. Once undercoated, they will look totally seamless.
Installation is not easy, especially given that my floorpans were replaced. A lot of trimming and bumping needed in my case. The rotisserie makes this a LOT easier. I can't imagine doing this on my back on a functional car! It can be done, though.
Start by putting the frame connector on a floor jack and moving the connector up into place. Mark areas that need to be trimmed. Try to get the ends well fitted. Expect gaps in the middle.
Once the ends fit nicely, tack weld into place. I had a bit of gap in the middle portions. Have soemone stand on the pans in the car and see how much gap you can get out. Small gaps, say an 1/8" or less, can be filled by the welds. You may have to bump the floor pans down in places to get the gap acceptably small. Weld short sections at a time.
At the rear portion of the connectors, you will have to squeeze the sides together to fit snug against the rear sub-frame. I used a torch to heat up the connectors as needed to get the sides to taper in.
This setup should be very solid.
