hmm on my box it only says for 35 to 45 engines
i dont think a 50 will fit in it
i just googled it too and the one that is the 40-59 is a arf mine was a kit (i you can call it that)
it was all stamped on plyboard mainly
but the one pictued for it is the same one but my box says 35 to 40
although mine is a precedent hi boy series II not the 40
may stick a meteor 40 or a os 40