Pay close attention to the photo marked "4-60L vs 5-60L".

As boof says, if it is a 1979 60L for A-series, it will have the dogleg pattern (reverse to the left).

But if it is a 1980-1982 it will have reverse to the right -- just like a 4-speed.

have ou looked thru this in regards to box markings .... wiki ... 5spd identification

not sure on specific markings on the box but there should be 6 shifter locations as opposed to the 5 on a 4spd box, 1st and reverse will be thru a gate across to the left ... 1st is across and down and reverse is across and up, get the sifter in those positions and then spin the input shaft and check the rotation of the output shaft ...

also if the box is in good condition then $550 is cheeeap !!!

i have had a 60 5speed box sitting in my shed. im 99% sure as i can find 5th. i have somebody intrested in buying the box. and am contemplating selling it. i have no idea wat cond it is in, but was told it was good. it has a custom mounting bracket made up. wat sort of money shud i be looking at selling it for. and how can i definately tell its a 5speed. i was told its worth round $550