If that is from a 77 it should have the starter on the right and the clutch fork coming out on the right as well. This is both as viewed with the front of the trans facing away from you, just like it would be installed in the truck.
If the starter is on the left and the clutch fork on the right it likely came from a 75 or older truck. Anything 77 or older will have a clutch fork with a pocket on the end for a push rod from a slave cylinder to fit into.
For an 81 you'd want a 78-82. The starter will be on the right and the clutch fork is on the left. The clutch fork will have a hook on the end for a cable.
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95 Isuzu Trooper Daily Driver
86 Isuzu Trooper reliable backup
77 LUV 2wd stock beltway blaster (resting)
79 4x4 LUV project: 2.6L, 5spd, 31s (eventually)
MEPR: Man, my 4x4 makes all other LUVs look good
