If it's an '87 as claimed the 8th VIN position indicates the Trim/Payload:
1 Base
9 XLS
F Custom, Metric Ton
P Pioneer, Std. Payload
R Pioneer, Metric Ton
S Chief, Std. Payload
T Laredo, Std. Payload
U Laredo, Metric Ton
the 4th position indicates engine:
B 2.1L Turbo-Diesel I4 (128 Cu. In.)
H 2.46L I4 1V (150 Cu. In.) Gasoline Domestic
M 4.0L I-6
W 2.8L V6 (171 Cu. In.)
Y 2.46L I4 1V (150 Cu. In.) Gasoline Export
and 6&7th positions indicate Drive/Bed length
63 4WD Comanche, 6Ft. Box
64 2WD Comanche, 6Ft. Box
65 4WD Comanche, 7Ft. Box
66 2WD Comanche, 7Ft. Box