As near as I can tell by my research, the Mustang II didn't have the 3.27:1 gear ratio available from the factory.
The only ones I can find are:
2.79:1
3.00:1
3.18:1
3.40:1
3.55:1
All ratios were available with or without limited slip, depending on year, and those were all for the Ford 8" rear end.
Of course, knowing which rear end housing you're using might help. 4-lug axles were used on six-cylinder cars from 1964-1969, and on all Mustangs (excluding the 1984-1986 Mustang SVO and 1993 Mustang Cobra) from 1974-1993.
Between those cars, there were also the 6.25" rear ends, the 7.5" rear ends, the early 8" rear ends, and the 8.8" rear ends, all available in 4-lug.
You could get certain 1979-1993 Mustangs with an available 3.27:1 gear ratio I believe, but I couldn't tell you for sure which years or which rear end housing (they used the 7.5 and 8.8 both through those years) they came in.
__________________ 1976 Ford Mustang II Ghia: 302 with a 600cfm Edelbrock carb, Edelbrock Performer 289 intake, Dynomax Blackjack headers, 2.5" exhaust with Flowmaster Super 44s. RJS 11-gallon fuel cell, C4 tranny, chrome 16" pony wheels, fuzzy dice, brown vinyl half-top, and painted in the tackiest color ever (harvest gold, that's why I call it "The Goldenrod").
Also have a 2003 Dodge Ram (lightly modded daily driver/tow rig/office/dining room/home away from home/workshop... I call it "The Big Blue Dawg".) | 
Rear End Question 
