There is a lot of this stuff out on the innerweb and some of those blog boys know WAY more than me about THIS. So, you may want to do (if you haven't already) a thorough search before taking anything I say as gospel.
I know that the smaller 5a55 will deliver approximately 58ml per stroke as compared to it's bigger brother the 5c60 at around 68ml...so you got that going for you...as in mo fuel. SOooooo. a swag would put the power increase POSSIBLE at anywhere from 20 to 40hp conservatively....depending....ON WHAT YOU SAY?...well...lots of things.
As in..turbo..blower..you didn't list a B in the headline so I'm guessing it is NOT bypass valved. It's simple really...if you can BURN the additional fuel EFFICIENTLY then you will gain the HP. If not...then you're just pouring money into the atmosphere. So, tune is important as well as air movement. Unrestricted intake + unrestricted exhaust is essential along with no induction leakage and well lubed T-bearings.
I would think, from what I've read, that this should be a good match and provide you with what you seek...a few more MPH on the water?...I'm guessing.
As far as timing these, I have to go with 1.460" because I don't really know. The way it goes when trying to "squeeze" some ponies out of these is that taller (1.465-1.470) advances the timing and shorter (1.450 etc...) retards. 1.460 is a "safe" place to start and, I would think, be near optimum. I read that the 5a55 is at 1.460 so I think the 5c60 would be there too since it's mostly a volume thing that is achieved internally within the injector body.
I know of no gearhead that EVER retards an engine to gain horsepower BUT it WILL run COOLER that way and THAT is pretty important. If you find that your exhaust gas temperature (EGT) goes high...900*F or higher consistently...you might consider making some changes to increase engine life and bring it back down under 800*F.
Of course, if you don't run pyros then you won't know anyway. So there's that.
Like I said, I'm no expert but you asked so I butted in.
Good luck.