Here's a thorough, (but not complete) list of American production cars ranked by their power/weight ratio.

1994-95Ford Mustang Cobra240335413.98
1989Pontiac Turbo Trans Am250346813.87
1993Ford Mustang Cobra235325513.85
2004-05Dodge Neon SRT4224290012.95
1986-90Chevrolet Camaro IROC-Z240310812.95
1993-97Chevrolet Camaro Z28275337312.27
2015-Ford Mustang300352611.75
1987Buick Regal GNX276324011.74
2007-08Pontiac Solstice GXP260301811.61
2015-Ford Mustang Ecoboost310353211.39
2005-10Chevrolet Cobalt SS260292611.25
2008-09Pontiac G8 GT361399511.07
2012-Tesla Model S420464711.06
2008-Dodge Challenger R/T375408210.89
1993-96Camaro Z28 SS305330610.84
1998-02Chevrolet Camaro Z28 SS325339610.45
1996-98Ford Mustang Cobra305307710.09
1996Chevrolet Corvette (C4) GS33032989.99
2009Pontiac G8 GXP41540509.76
2004-07Cadillac CTS-V40038509.63
2014-Chevrolet Super Sport41539759.58
2008-11Tesla Roadster28827239.45
2003-04Ford Mustang SVT Cobra39036659.40
2006-09Cadillac STS-V46943949.37
2000Ford Mustang SVT Cobra R38535899.32
2004-06Pontiac GTO40037259.31
1997-04Chevrolet Corvette (C5)35032459.27
2009-Chevrolet Camaro SS42638609.06
2008-Dodge Challenger SRT847041708.87
2015-Ford Mustang GT42037058.82
1990-95Chevrolet Corvette (C4) ZR140535128.67
2006-09Cadillac XLR-V44338108.60
2015-Dodge Challenger SRT8 39248540828.42
2013-14Ford Mustang GT42034838.29
1992-95Dodge Viper RT/1040032848.21
2012-13Ford Mustang Boss 30244436318.18
2005-13Chevrolet Corvette (C6)43033117.70
2001-04Chevrolet Corvette (C5) Z0640531157.69
2009-15Cadillac CTS-V55642137.58
2014-Chevrolet Camaro Z2850538207.56
1996-02Dodge Viper GTS45033757.50
2014-Chevrolet Corvette (C7) Stingray45532987.25
2009-Chevrolet Camaro ZL158041207.10
2016-Tesla Model S "D"69148236.98
2015-Dodge Charger SRT8 Hellcat70747576.73
2015-Dodge Challenger SRT8 Hellcat70744496.29
2006-13Chevrolet Corvette (C6) Z0650531306.20
2003-07Dodge Viper SRT1050030806.16
2005-06Ford GT55034856.34
2013-14Ford Shelby GT50066238505.82
2007-10Dodge Viper SRT1060034505.75
2015-Chevrolet Corvette (C7) Z0665035245.42
2013-Dodge SRT Viper64034315.36
2009-13Chevrolet Corvette (C6) ZR163833335.22
2010Dodge Viper ACR-X64031904.98

Note: I'm not too sure about the street legality of the ACR-X

Now all those high powered cars of the 1960's should have impressive power/weight ratios as well. The problem is that they're rated in gross horse power, and converting them to net is anybody's guess. In 1971 they started rating cars in net as well as gross so we can get some idea of what the cars would have been rated. I've added an estimated net rating based on a ~20% loss, which may or may not be accurate. The website I used didn't seem to like keeping info on Pontiacs or Plymouths.

yearmodelgrossnet
1965Avanti 32711.1713.96est
1957Ford Thunderbird 312 Supercharged11.1713.96est
1970Buick GSX Stage 110.7713.46est
1970Ford Torino 429 Cobra Jet10.6513.31est
1957Chevrolet Corvette 283 F.I.10.2812.85est
1971Chevrolet Chevelle SS 454 (365hp)10.2713.16
1969AMC AMX 390 (315hp)10.2312.78est
1965Chevrolet Nova SS 327 (300hp)10.1212.65est
1968Ford Mustang GT 428 (335hp)9.9012.38est
1969Dodge Coronet Super Bee 440 (390hp)9.8612.32est
1971Ford Mustang 429 Cobra Jet (370hp)9.7312.16est
1969Chevrolet Camaro SS 396 (375hp)9.7112.14est
1971Dodge Challenger 440 (385hp)9.7111.32
1971Chevrolet Corvette 350 (330hp)9.6911.63
1968Dodge Dart GTS 4409.4111.76est
1969Dodge Charger Daytona 426 (425hp)9.3311.67est
1964Dodge Polara 426 Ram Charger8.7710.96est
1971Dodge Challenger 426 (425hp)8.7710.65
1963Chevrolet Biscayne 4098.6010.75est
1970Chevrolet Chevelle SS 454 (450hp)8.3210.40est
1968Dodge Dart GTS 4268.2810.35est
1964Ford Fairlane Thunderbolt7.889.85est
1971Chevrolet Corvette 454 (425hp)7.7110.09
1967Chevrolet Corvette 427 (435hp)7.689.60est
1965Shelby Cobra 427 (410hp)7.209.00est