Do you have an SS or an LT1? Your sig says the latter, but the title of your post says SS. It's also difficult to answer such questions on a forum where it's unlikely that people who had your exact configuration would want to do the same exact mod.
Anyhow, if your current front tires are 245/40/20, it's unlikely you can go up to 275/40/20, as that's a full inch taller and the strut perch is already pretty close with a stock setup, I don't think there is an extra half inch in it, at least not without spacers.
For reference, here is how much clearance I have with 285/35/20 PS4S tires that are only 0.2" taller than stock (I also have MRC), see picture below.
Your setup would add a total of 0.8" to this already borderline arrangement, there sure isn't 0.4" of extra space there. If you're willing to use big spacers, then of course it will work, but that's a bit of a rabbit hole...
The rear you want is also ginormous, even taller than a 305/35/20 configuration, not sure why you'd want that, although I think there is enough space in the well with stock wheel widths. You might need to relocate body wire harness on the driver side, see this thread for details:
https://www.camaro6.com/forums/showthread.php?t=485975 (not entirely sure this still applies to 2020 cars, but it's likely).