Mostly. The suspension setup is better too, but it's mostly the wheels.
Technically it is how it has been classed by SAC - saying "pushes it out of FS" makes it sounds like it has FS illegal part which isn't the case - it's where people making classing decisions decided it belongs. For better or worse.
No one will care about your rails, shifter - unfortunately someone might although I doubt it on a local level (if someone protests you it would actually be funny). Looks like new M5s have not been classed since no one probably asked for them to be classed. Where would they fall, who knows but I wouldn't worry about it too much if it is was your first autocross - rather focus on driving improvements. Shifter I think puts you in a Street Touring, where the clutch line puts you - no clue - but it makes way more sense to run CAM-C than the actual class mods put you in.
I think the SAC is going to be forced to go one of two directions if FS keeps shrinking - either move the overly expensive/rare BMWs out of FS or bring the faster special-edition muscle cars out of BS/AS and into FS.
After further through my absolutely wild out of my ass guess is that the '19 M5 would end up in BS if someone asked to class it.
I probably should have said "at least BS". ZL1 1/LE is in SS after all, GT500 should get burried (given inaccesibility, ADM and all) so would say higher than that.
Did you add the magnarides to a PP1? I thought that was only part of PP2.
MagnEride is a separate line-item as long as you have PP1. It's included as part of the PP2 package which also includes the wider wheels+tires, supposedly enhanced MR tune for Track-mode, and the different rear spoiler.
Magneride was always an option on '18+ PP1. I think Dick R here was one of the first one that ordered his this way, mine was a leftover purchased late in 2018.
In terms of the M5 awd with 617 hp in FS, I don't see it classed there but could easily see it classed in FS as it is 4300#. While it can accelerate very fast, autocross is more about tire to weight ratios which it takes a huge bite on. Despite that, I'd guess it will land in BS as it still tops $100k price tag new. As for your mods, some are not permitted and I'd never encourage anyone to compete in a class with unpermitted mods. OTOH I would not protest at a local unless it was an extremely ridiculous mod (ex. interior removal in street -- yes I've seen it).
Disclaimer -- I am no longer in FS as I sold my 2011.75 BMW M3 ZCP (of which there were several thousand built between 2011-2013) for less than $22k so I would characterize the car as overly expensive or rare. People have significantly stopped coming to Nat's in pony cars either out of the perception they can't compete or have just chosen to run in CAMC with more mod allowances. That's the reason for shrinking numbers. I've always felt that Leeder could have won in 2018 but didn't drive to his best. They can't move the M3 out for 2020, and it is fair more likely that in 2021, you'll see the PP2, probably the SS1 1LE, and maybe the GT350 although that's less likely. That said, I could see them also move the next gen M3/M4 down as well. All this will not bode well for folks who have PP1 or a regular GT unless you can do a full package update easily.