ok, here's my try at this...
all transmissions are 6-spd , all cars have equal trq to hp, trucks have 15 more trq than hp.
Aveo: like now, maybe add 3-door and hybrid
Cobalt: delta, FWD, sedan, coupe or 5-door same price
LS: 140hp Ecotoec, 13k, manual or auto
LT: 145hp Ecotoec, 14.5k bit lux, manual or auto
LTZ: 170hp Ecotec, 16k real lux, auto only AWD opt.
SS: 220hp super. Ecotec, 20k sports, manual or auto
SS-AWD: same as SS, but 22k and AWD
Camaro: large Kappa (2+2) coupe/convertible
LS: 245hp 3.9L, 20k, auto or manual
SS: 310hp 5.3L, 25k, auto or manual
SS Z-28: 390hp 6.0L, 31k, auto or manual, more lux/canyon carver, AWD opt.
SS IROC: 410hp 6.0L, 31k, manual, mostly drag racer, least lux
Malibu: epsilon II, FWD, little bigger than camry, Maxx add 1.5k
L: 175hp ecotec, 17k, very basic, auto only
LS: 200hp 3.5L, 20k, bit nicer, manaul or auto
LT: 210hp 3.5L, 21k, more lux, auto only
LH: 245hp 3.5/hybrid, 24k, auto only, AWD std.
LTZ: 245hp 3.9L, 24k, manual or auto, AWD option
Chevelle: SWB Zeta sedan or coupe, slightly smaller than malibu but nicer
LS: 245hp 3.9L, 21k, auto or manual
LT: 250hp 3.9L, 22k, more lux, auto only
LTZ: 300hp 5.3L, 26k, auto or manual, AWD option
SS: 380hp 6.0L, 31k, auto or manual, sedan only, AWD option
Impala: LWB Zeta sedan, fullsized
LS: 245hp 3.9L, 25k, auto or manual
LH: 300hp 3.9/hybrid, 28k, auto only, AWD std.
LTZ: 320hp 5.3L, 29k, auto only, AWD opt.
SS: 400hp 6.0L, 33k, auto or manual, AWD opt.
Monte Carlo/El Camino: LWB Zeta, basically impala coupe or truck
LS: 245hp 3.9L, 26k, auto or manual
LTZ: 320hp 5.3L, 30k, auto only, AWD opt.
SS: 400hp 6.0L, 34k, auto or manual, AWD opt. El Camino only
Vette: keep as is
Colorado: same chassis, but grow a bit, 4WD same price, 1.5k for crew cab
LS: 200hp 3.5 I-5, 17k, manual only
LT: 220hp 3.5 I-5, 18k, auto or manual
LH: 265hp 3.5/hybrid, 23k, auto only, AWD (not 4WD)
Z-71: 275hp 4.2 I-6, 23k, auto or manual, off-roader
SS: 290hp 4.2 I-6, 26k, manual only, lowered, sporty, AWD opt.
Equinox: theta chassis, same body as now, AWD std.
LS: 200hp 3.5L V-6, 19k, auto or manual
LT: 210hp 3.5L V-6, 20k, auto
LH: 245hp 3.5/hybrid, 23k, auto only
LTZ: 250hp 3.9, 24k, auto or manual
Trailblazer: moves to Colorado crew chassis
LS: 275hp 4.2 I-6, 23k, auto or manual
LT: 275hp 4.2 I-6, 24k, auto only
LH: 285hp 3.5/hybrid, 26k, auto only, AWD
SS: 320hp 5.3L V-8, 31k, auto or manual, lowered, AWD opt.
Sliverado 1500: new bigger chassis, 3/4 and 1 ton also avail, crew is 2k more
L: 275hp 4.2 I-6, 25k, auto or mmanual only,, very basic work truck
LS: 320hp 5.3L, 29k, auto or manual
LH: 315hp 4.2/hybrid, 29k, auto only, AWD only
LHZ: 350hp 5.3L/hybrid, 32k, auto only AWD, most lux
Z-71: 360hp 6.0L, 33k, auot or manual, off-roader
SS: 400hp 6.0L, 36k, auto or manual, AWD opt.
Tahoe: based off 1500 ext. cab Silverado
LS: 320hp 5.3L, 32k, auto or manual
LH: 315hp 4.2/hybrid, 32k, auto only, AWD only
LHZ: 350hp 5.3L/hybrid, 35k, auto only AWD, most lux
Z-71: 360hp 6.0L, 36k, auto or manual, off-roader
SS: 400hp 6.0L, 39k, auto or manual, lowered, AWD opt.
Suburban: based off 2500 crew cab (not just long tahoe)
LS: 335hp 5.3L, 36k, auto or manual
LH: 375hp 5.3/hybrid, 39k, auto only,AWD only
LT: 375hp 6.0L, 40k, auto only
LTZ: 400hp 6.0L, 43k, auto only, most lux
Avalanche: off-roader SUT based on 1500 crew, bigger than tahoe, optional retractable rear section and 3rd row for 1.5k
LS: 335hp 5.3L, 35k, auto or manual
LT: 375hp 6.0L, 39k, auto only
Z-71: 400hp 6.0L, 42k, auto or manual
wow, that's hard!! now for pontiac, buick, saturn, GMC, saab, caddy...

i think i found a solution to the chevelle/monte issue... let me know what ya'll think
also, anyone from SC/georgia/NC/tennesse going to the SC auto show in greenville this weekend??