You cannot do directly what you are thinking....A SFR is an actual 8 bit physical register on-board your 8052 or derivative part. As such the "sfr" nomenclature is used in the compiler to inform the compiler of the existence of this physical register.

An SFR is not a random collection of bits, be they port bits or otherwise, that one has decided to group together.

If it is needed, by the software engineer, to have a group of 8 port bits grouped together so that software can be efficient in some tight algorithm then it is necessary to work closely with the hardware engineer to get these bits assigned to the same physical I/O port of the microcontroller, such as all on P3 for example.

Hope this helps
Mike