Within the 45-series Land Cruisers, my recollection of "LPB" is that the initial designation was: FJ45-PB, and FJ45L-PB, "L" meaning LHD, with the home-country original Japanese RHD vehicles not designated with an "R". The "P" meant "Pickup" body, and the "B" was for the long-bed longer wheel-based vehicle, to differentiate it from the short-bed version. There were variations throughout the years of production often with additional letters to designate specific differences. The so-called "45LV" or FJ45LV you will see is the LHD version of the FJ45V, the Van or wagon style body. In Japan the RHD version would simply be a FJ45V. The short, rounded-corner 45 pickup trucks should be called FJ45P and FJ45LP, since I believe they were the first, or "A" versions of the pickup body style. Later FJ45 trucks also came in the Troopy bus style. The Brazilian Toyota factory produced a standard long bed pickup, an extended cab 2-door pickup, and a 4-door crew-cab pickup, but they were designated differently and carried Mercedes-licensed diesel engines. And then there are the F, B, and H leading letters to designate engines and fuel-types. Or so I understand it.
If I am incorrect in any of this, undoubtedly I will soon be admonished.