Well, FWIW, a 302 can be bolted right into a Mustang II (if it didn't already come with one stock), and being that they don't weigh diddly-squat, I'd imagine dropping in a stock long-block from an '87-'95 5.0 Mustang with a decent cam, intake, and carb could make the thing VERY fun to drive for not a whole lotta money ... although, of course, you would wanna upgrade the rear end, trans, and brakes at the same time unless you feel like breaking stuff and/or running into walls...

But that's all a moot point, as stock for stock, they were the most pathetic of all V8 Mustangs - 120 horses, woooooo!
What about the '83 Mustang GT where they brought back the 302 after a brief hiatus? What about the 1996 Cobra with the first DOHC 4.6L in a Mustang? (The SOHC GT's 4.6L was certainly nothing to crow about.)
II's did not have the 302 in 1974, the first year they came out. John Q Public kinda freaked that there was no V8 in a Mustang and in 1975 they offered the 302 with something like 120-140hp. The nose of the 75+ cars are slightly longer than the 74 in order to accomodate the V8.
The 83 GT is meaningless...the only 83 that means anything is the convertible. The 82 GT is the important one...introduced the 5.0 HO and brought performance back. The DOHC motor in a Mustang is only important to people like us who care about Mustangs...
My top 10 Important Mustangs...in no particular order...and not necessarily my favorite ones, just ones that are meaningful in the history of the Mustang
1964.5 Mustang...got it all started
1965 Fastback...most popular body style is introuduced
1969 Mach I...first true performance package
1974 Mustang II...flew the Mustang flag through the dark ages
1982 Mustang GT...brought performance back out of the dark ages
1987-1993 Mustang GT & LX 5.0...possibly the largest and most enthusiastic following of any generation of Mustangs
1993 Cobra...SVT launched
2003 Cobra...Pushed Mustang performance over-the-top to Corvette status
2005 Mustang...Mustang fever all over again
ALL Tuner Mustangs...namely Shelby's, Saleen's and Roushes...always kept things interesting, more specialty versions built than any other car
Other important cars include the Boss 302, 351 and 429, 1967 GT/GTA 390 (first big block Mustang), 1984 SVO, 1985 GT, 1994 GT, 1995 Cobra R, 2000 Cobra R, 2007 GT500