No, they're different. the main "box" bit is more or less the same (although there might be a few cosmetic differences, nothing that won't stop you bodging it to fit) but the front face where the tunnel screws on, is a different shape (because the tunnels are different)
R380 is tunnel is bigger. if the front face of your LT77 one is ok, you could cut it out, in a large "square" around the tunnel fixings, then graft it onto the front of the R380 tunnel (pop rivet the square plate on)
Floor plates are decided by which tunnel you use. they're all the same when i comes to the front flange of the seatbox.