Here's what some of the codes mean:
A39 - Police Package
F43 - Reinforcement for spotlight
F88 - Engine oil cooler
G11 - Tinted glass all
H51 - Single A/C with heater
N41 - Dual exhaust
D36 - Heavy duty 727 trans
E86 - 440HP engine
Y39 - Special order

The 999 codes were used when the cars were custom painted as per the
police department's color scheme. The 2nd digit being a "H" isn't
unusual for a '75 and newer police car. The A38 makes it a police package car. I had a '77 Grand Fury from the North Carolina State Police that had a "H".