Are you going to use a set of ST4S crankcases? The SPS cases are not bored to take the 888 swingarm pivot bearings.
I have been thinking about putting an SPS engine in my SP3 and keeping the original engine safe from track days. I also prefer the extra mid range torque of the SPS, and the top end as well!
All the best,
Mike
851 SP3
996 SPS
Brutale