Personally, I would go with wiseco pistons on eagle rods. It seems to be the majority favorite of engine setups. From experience with them, i would never change my setup for anything else.

Agreed, the wiseco/eagle Combo seems to be the preferred route for the Dsm community

You really need to give us more of a goal for this build. What HP are you shooting for, as well as fuel type, ect..

You will be able to make just as much power on the 8:3.1 as any other compression ratio only at a higher boost level. They give you that extra cushion in case for some reason you have a screw up in your tune somewhere. With a higher compression, you pretty much have to be spot on. They are more forgiving but in return you are have to run more psi.
The Eagle's are a good all around rod, and really take a hell of a beating. They are the chosen combo because it works. I'm sure the manley's are just the same. With a good builder assembing the motor correctly, any off the shelf combo will work until you get into some serious power. At this point, you have to step up to either an I-beam, Aluminum rod, and a better piston. IMO if you are under 700whp, with a good tune, the reg. Wiseco's or Manley pistons on either h-beam will work. Take your pick. If you were a stroker, I would say to look into the HD version as the reg. stroker piston's have been known to have random cracking issue in the skirts. IMO any engine over 450whp I would open at least once a season to check bearings, play, cracks, ect..

Thanks for your opinions!

I am ultimately shooting for 500 whp, but this will be a little while after completing the build. And I will just be running 93 octane.

I understand the tradeoff of compression and boost, I guess the decision I'm trying to make is the tradeoff between a slightly higher compression with slightly better spooling characteristics, or simply adding a lb of boost or 2. I would also like the car to be as un-sluggish as possible.

I have seen that many performance manufacturers carry a 9.0:1 piston for the 4g63. This is much higher than I want to run, but I figured 8.5:1 would still be pretty safe. This is the factory compression, which I have imagined would make tuning a little easier.

But I'm still a little undecided.

Wiseco makes an 8.5:1 piston. Eagle/WisecoHD's is what I use.