The supra is a heavy car. But not much heavier then most cars are.
Only a few hundred pounds heavier then allot other cars. So I wouldn't be to concerned with its weight.
They will move quickly enough, and you could always strip the car down to reduce weight if you wish. You could replace windows with plexi glass and so on it you want to. However not sure if that is legal in CANADA, it isn't for street cars in NC, USA. But I have seen it done.
The Supra is a good car I love mine and it's a 1988, I have spent allot of money on it in the past 3 years I've owned it. However even though I haven't finished tuning it, she will get up and go.
Before mine blew a HG I was racing it against V8 mustangs and the like. With some wins and a few losses. But never got out run by an integra, civic, focus, or eclipse. But never raced any that where modified though.
I have owned 3 Mustang V8's (89,91,92), a Corvette (96), Eclipse GSX (92), CRX Si (91), RX7 (91). The supra by far is the best overall of the group, not to mention the oldest of the group (1988).
If you’re looking for Turbo supra you should know they only made turbo models (232hp) 87-92 (not in 86.5) you will enjoy it no matter which one you get. Just take care of it and it will take care of you.
As for your 1/4 mile question. That depends on allot of things not just the cars, or there power.
Power transfer and driver skill will determine almost all races.
In other words if you have a perfect reaction time on the strip, and you can launch your car perfectly, and the other drive can not then you will win every time even if you have a little less power.
For example one of my first races in a 89 GT mustang (I was 18), I lost 3 times before my father finally told me why, since I couldn't seem to learn it. He told me one simple thing "If you’re spinning your not winning". I couldn't launch the car so I was loosing to older less powerful cars. I would drop the hammer off the line and spin through 1st gear and into 2nd gear, mean while the other drivers would launch correctly and start moving down the track while I was spinning my tires in one spot for 1 and 1/2 gears. So I would be a car length or more behind when I started moving.
So if you can launch your supra better then the integra driver you will win for sure. If you launch the same, then you will still probably win
But only a real race will tell us for sure.
Good luck finding your Supra, it is fun shopping, and getting one.