I think you're options are pretty clear.
A 6th Generation ZL1 in reality is going to be out of your budget, they go for around $70,000 - $75,000 for a 2018 model. But ideally you want a 19+ ZL1 as they fixed a few cooling issues the 18s had.
A GT350 is a fantastic option. I've had the privilege of driving one a few times. They are an amazing drives, not the fastest things in the world due to their low torque, but dynamically the car is incredible. So engaging, so much fun, very thrilling and they sound incredible. Just make sure you buy a 2017+ with the electronic package. The 2016 models you had to choose either the track package (magnetic ride suspension, extra coolers + extra goodies) or the convenience package (a proper infotainment system). For the 2017 year the Track package become standard and you only had to choose if you wanted Recaro seats or Leather seats and if you wanted the extra Infotainment.
A Camaro 2SS 1LE is a excellent option too (Yes, I'm biased). Significantly cheaper than a Mustang GT350 and basically as fast around a track and drag strip.
Two really nice options:
a 2018 2SS 1LE in Edmonton $45,000
https://www.autotrader.ca/a/chevrolet/camaro/edmonton/alberta/19_11521520
a 2019 2SS 1LE Tuned (About $8,000 of mods)
https://www.autotrader.ca/a/chevrolet/camaro/fergus/ontario/19_11568922
The biggest challenge with the 1LE SS is they are pretty rare so finding a really good one, especially here in Quebec is quite difficult.
Your third option I see is a Mustang GT Performance Pack 2
Basically a Mustang version of the 1LE, you can find these a bit easier
Coming back to it though. If you can afford one my preferences for a $70,000 budget would be:
1. Chevrolet Camaro ZL1
2. Ford Mustang GT350
3. Chevrolet Camaro 2SS 1LE + Lots of mods ($20k worth of mods)
4. For Mustang GT Performance Pack 2