What fuel do you plan on running?

How will you be tuning the car?

Also, the higher compression will help you squeeze a little more power out of high octane fuels at the cost of a much smaller tuning window.

I run 9:1 compression in my car, and it's fairly easy to tune up to 40psi on e85. I can also run 25psi on pump gas if I have to. You will have a tough time running any decent boost and timing with 10:1 and pump gas.

I'm going to be running e85 and tune with dsm link. I might do 93 octane once In a while

Theres no reason to ever buy 8.5:1 pistons any more. Todays feul is so different than what it was in the 80s and 90s that we should all be running 10:1 and i would do 12:1 in an e85 turbo car.

I am building a 10:1 wiseco holset 6 bolt set up for regular pump gas (we only get 91 oct here) right now actually.

The octane, octane rating, hasnt changed since the 80's and 90's... 91 is still 91 etc. I'm with @donniekak here, been fine with 9:1 and probably will still stay 9:1 or even 8.5:1 for more heat energy to spool. I run e85 only and 40psi on 6466

Thats not to say 12:1 isnt fine on e85, it is. Your just more limited on timing then You would on lower CR

I highly recommend checking your math on final compression ratio for you application.

The high compression is really only slightly better for off boost power so I'd stick to the lower compression pistons for the better tuning window. Also, Wiseco mislabels their CR for our cars. Those 10:1 pistons are much lower in real world application. They are actually close to 9.5:1. The 8.5: are usually 8.3:1 and lower.

From someone that runs a static CR around 11.3:1. Go with the 8.5:1. They are tried and true.

Ok the 1400hd in 85 bore are 8.45 and the 1400hd e85 are 9.63 in the standard bore

FYI. You should be using a gasket crush thickness of .051" and also remember you will mostly likely not be at zero deck unless you asked your machinist to do so. Most likely the pistons will be sunked in lowering CR a bit more.