3917215....67-68...oval..CLOSED..396, 427, 101cc chamber
Bore Stroke 4.094 bore 3.76 stroke 400 is 4.124
A +.030" 4.094" bored to 4.124 with the ZL2240NF30 -21.00cc piston will give you approx a 10.2:1 Static Compression. A 278S(or SR)-10 Cam should give you approx an 8.2:1 DCR and push you easily to 6500rpm - NICE for 91 Octane ;o)
A +.030" 4.094" bored to 4.124" with the SLP-L2242F30 -38.30cc piston will give you approx a 12:37:1 Static (Too Much for Pump Gas)
And Yes; both Piston and Heads are Closed Chamber and compatible. You have to watch out using Open Chamber Heads over Closed Chamber Pistons as you usually have to relieve the Combustion Chamber and done all the time. You can not use Closed Chamber Heads over Open Chamber Pistons.
Play around with P. Kelley's DCR Calculator to help Select a Cam: http://www.empirenet.com/pkelley2/DynamicCR.html
You should always CC the Heads to insure the Combustion Chamber Displacement and if you do not 0-Deck for a .038" Composite Gasket use a .018" Steel Shim Head Gasket keeping Quench Specs between .034" to .044".
A Holley 750DP/Edelbrock RPM with Quality Roller Rockers and you're Flying ;o)
PS: If you go for Roller Rockers, you need 2" ARP Rocker Studs. Stock OEM Studs are probably the main reason the Roller Rocker Failure.