Picked up a total rust bucket but still had some good parts + 8.8 with 4.10 TL rear. Even has the headliner, all good TR trim, TR glass, quarter windows, doors, black/tweed High back buckets and rear seat, 3 piece spoiler, 4 black seat belts and a bonus T Top bag and some other parts. Still have to remove the contents to see what is actually there but no front end or most interior plastics.
Here is what I decoded so far:

1FABP15A2BF233959

MUSTANG = Mustang model line
233959 = 133,959th 1981 Ford scheduled for production at Dearborn Assembly
61R = Mustang 3-dr sedan (hatchback)
A = non-turbocharged 2.3L engine
TR = T-roof
0821 = body & paint rotations #0821
177 = Medium Pewter Metallic exterior paint color
TT = Black lower tu-tone
DF
ST
AC = manual air conditioner
05 = YES rear defrost, YES rear wing, NO rear louvers, NO rear washer/wiper
RA = road abrasion coating (lower bodyside protection)
HB = heated backlite (rear defrost)
CBR = Cobra package model/trim level
07 = rear-facing non-functional full length hood scoop
V = visibility (light/convenience group)
ELECTRIC
A = Black interior trim color