Assuming these are the correct parts...
https://www.jegs.com/p/Mopar-Perfor...-Stage-1-Performance-Springs/2178463/10002/-1
https://moparonlineparts.com/dodge-challenger-mopar-lowering-springs-p-5821.html
https://store.mopar.com/accessories...e-suspension_upgrade/suspension_P5155436.html
"
When fitting lowering springs (312-P4510854) on 2006-Newer 300C, Charger R/T, Magnum R/T & Daytona vehicles equipped with Sachs Nivomat self-leveling rear shock absorbers, a rear shock change is required for proper appearance."
There doesn't seem to be a history of issues with the SRT Bilsteins - keep in mind that most Bilsteins are a mono-tube shock, and not a twin-tube design (like Belltech or KYB) that has an internal reservoir to displace fluid when lowering, so too low is going to cause control issues but there is a safe range based on loading (five adults, lots of crap in the trunk, all the options checked at the time of ordering). So, doubt they aren't compatible.
And to quote
@TrackDay:
"Stock Challenger springs - 313/778 front/rear lbs/in (single rate spring)
MP springs - 240-337/514-828 front/rear lbs/in (progressive rate spring)
I have seen no data about load vs. compressed length on the MP springs. With progressive springs it's hard to know if they are really starting at 240 lbs/in at front compressed ride height. I think it's doubtful. Note, that at full compression they are a little stiffer than stock. The progressive spring rate ensures the ride is not much if any stiffer than stock springs, both in the front and rear.
I think the main thing that is an advantage with these springs is the lower ride height gives us a little more negative camber and lowers the car about a half inch for better handling as well. If you're purely going after better handling I expect the firmer front KW springs (413-536 lbs/in progressive rate) are a benefit, but the rear KW springs have less spring rate than the MP (590-719 lbs/in)."
Plus, consider that an alignment will be needed to get the tires back into spec.