Not sure how you figured 8.4:1, unless the pistons are deeply dished. KB202 flat top with a 3cc valve eyebrow will make 9.317:1 SCR when used with 101cc heads.
KB Pistons for Automotive Applications
Most any of the special pistons with a small pop-up to work with the closed chamber heads will make too much SCR for pump gas. Here's the SRP offering with a 14cc dome...
BIG BLOCK CHEVY - CLOSED CHAMBER - SMALL DOME PROFILE - JE Pistons
In my opinion, the 3cc pistons mated with a cam that closes the intake valve at somewhere around 35 degrees ABDC would make a DCR of ~8.236:1 that should run well on pump gas and make good power without detonation. I don't like recommending flat tappet cams, but will show you an example of what I might use as far as cam timing.....
Excellent midrange torque and HP,good idle, daily usage and offroad, towing, performance and fuel efficiency, good w/smallplate nitrous system, 2600-3000 cruise RPM, 8.75 to 10.5 compression ratio advised.
Good w/centrifugal or small Roots supercharger, 8lbs. maximum boost w/8.5:1 maximum compression ratio advised.