Frame Connectors?
I used the mopar performance bolt on deals.Kinda cheapo, but they work.
Had to use washers to shim the fronts a bit and drill some holes to bolt the rear sections in.
Then I welded them wherever they touched the floor and welded the front and rear areas fully at the perimeters.
They make better, perfect contour fit ones for E and B bodies I believe, but I'm not sure about A bodies yet, and some guys fab up their own, cut the floor pans and go crazy with them.
I'm sure someone will chime in with some more answers for you.