Caliper swap, spacers and a bit of grinding needed for the steelies to fit. I've only seen two examples on the interwebs where it's been done. This includes the cool example from @NoGaBiker

It's a shame there is so much work needed to fit steelies. I wouldn't want to run spacers, least of all run them with steel wheels.

265/70 is 32.6"
275/70 is 33.2"
285/70 is 33.8"

@Saltek Motorsports have an excellent how-to on trimming the wheel liner to fit bigger tires. Seems like a no lift, trim only, option exists for the 33.2" option. Possibly the 33.8"

 

I'll be testing this out in Jan/Feb with 275 70s and documenting it somewhere on the forums. I have a p300 on order and will be ordering aftermarket 18s so no need to touch the calipers.

 

On a 2 inch subframe lift but have seen some references here doing it with a 1 or 2 inch rod lift. Either way you need to move the aux radiators and trim the front bumper.

 

@GavinC What's the steel versus alloy factor here regarding spacers? I'd also like to keep my 18" steelies while adding more off-road-worthy tires. Thanks.

 

It has been a while since I was delving deep in the nerdy weeds on this one but this is my rudimentary understanding as to why it’s il-advised.

The steel wheels have a tapered interface with the lug nuts that gets them nice and snug against the steel hubs. Steel on steel on steel.

Add aluminum spacers and now you’ve introduced a softer mating surface.

Steel nuts with a tapered interface to the steel wheels when torqued to spec may get the wheel to bite into the soft aluminum spacer.

Over time this will degrade your hub-centric mount and introduce the potential for movement.

I’m sure someone with more knowledge than I can blow this concern out of the water but that is my understanding and it makes sense to me with my limited grey matter.