I think they'd look good
There's an Orange M3 GTS parked next to my 335i and I've been using it to visualize which body panels to swap out. I would stick to the M3 front bumper, M3 Sideskirts and Mtech Rear bumper if you want to do quad exhaust. The M3 rear bumper, hood, and side marker turn signals look a little tacky on a 335i unless you go for the full wide body conversion.
I've been dealing with Ronno over at Cargym and he's been super helpful, patient, and considerate. I plan to purchase a replica kit as speced above from him as soon as I've replaced my OEM wheels with GTS replicas and figure out which coilovers to get . If you're worried about fitment on the sideskirts search for "Former_Boosted_Is M3 Sideskirts" in the DIY section. The ones he reviews fit perfectly. Once you get the name, check with Ronno if he can source them for you so you don't have to pay crazy US shipping charges!
Hope that helps! Just out of curiosity, what did you decide regarding your JB4? I just ordered a Procede, so if you decide to keep it, it would be interesting to drive our cars back to back