In terms of the 3000GT/Stealth cars, here is a description of what cars had what motor when:
From '91 through '96:
Dodge Stealth:
Had 4 models, with production ending in '96.
Base model: 3.0L SOHC V6 with 164 bhp
ES model: 3.0L DOHC V6 with 222 bhp
R/T model: 3.0L DOHC V6 with 222 bhp
R/T Twin Turbo: 3.0L DOHC Twin Turbo V6 with 300 bhp (upped to 320 bhp in 1995)
Mitsubishi 3000GT:
Had 3 models to begin with, significant changes occurred in '97.
Base model ('91-'96): 3.0L DOHC V6 with 222 bhp
Base model ('97-'99): 3.0L SOHC V6 with 185 bhp
SL model ('91-'99): 3.0 DOHC V6 with 222 bhp
VR-4 model ('91-'94): 3.0L DOHC Twin Turbo V6 with 300 bhp
VR-4 model ('95-'99): 3.0L DOHC Twin Turbo V6 with 320 bhp
Aside from the HP differences, the cars had other suttle differences (i.e.-'95 saw the VR-4 go from a 5-speed Getrag transmission to a 6-speed transmission). I owned a '95 3000GT base with the DOHC motor. I actually raced an SVT tour once (long time ago and legit at a track))and we were pretty even through the 1/4. I can't give you exact times or anything, but it was fairly even.
As I recall, back in '92 Road & Track ran an article pitting a '92 Stealth ES against a '92 300ZX base. I do remember the Stealth ES pulled a 0-60 time of 7.1 seconds (manual). If this person has a MTX car, they will stay pretty close with you, but only if it is the DOHC motor. If it is a SOHC, or a car with a DOHC ATX car, you will have no problem. The ATX in the 3/S cars is not the ideal mating of motor and transmission. In fact, the only combination that is probably worse is putting the Tiptronic auto trans with the 1.8T motors in the VWs and Audis.
Oh, and if you are at a stoplight and you need to tell the difference between a 3/S with a SOHC motor and a DOHC motor, there are some easy methods without popping his hood:
If the car is a Stealth from '91-'93, it will have flip up headlamps as will a 3000GT. The DOHC Stealth cars (including turbo models) only came with factory fog lamps from '91-'93. Thus, if you don;t see any factory fogs, its a base model, and you will have no problem. '91-'93 3000GTs all have the DOHC motor, so it will be more of a challenge.
'94 saw the flip up headlamps abandoned for the "samurai" (their term, not mine) fascia with the quad projector headlamps. Same specs as the '91-'93 models, except the aforementioned boost in HP on the '95 and '96 turbo models.
'97 is where it gets tricky on the 3000GTs (as the Stealth was no longer made). The '97 and '98 models have the "arc" spoiler similar to the Eclipse. The base models have a wheel design (16") that has 3 main divisions, with 2 "spokes" per division. You will have no problem with this one, as it is the SOHC motor. The SL (DOHC motor) has a wheel design (17") with,I think, 7 "blades" (kinda similar to the SHO "slicer" wheels). The VR-4 models have 18" wheels that have their own look. The '99 models went to a "combat" spoiler, with wheel designs remaining similar I believe. Of course, if they have custom wheels, it becomes more difficult to tell...
Well, hope this helps in the evaluation of potential contest. I know I wrote WAAAAYYYY

too much here, but I figure it always helps to have too much info. as opposed to too little! LOL