Thanks for all advice Guys. R3 or Ritter is not an option for me unfortunately. Price + shipping + taxes to ship to Brazil is unbelievable expensive. Best pump gas in Brazil has 96 oct and 30% of ethanol. Currently I`m running with 12.0CR on this Pump Gas, Cometic head gasket and ARP bolts. No Issues so far. This engine has a 318 block, 3.58 Scat Series 9000 and overbored to 4.000". After all machine works I did a sonic check at the cylinders bore and the thin wall measure that I found was 0.148".

I'm looking forward to use Victor Heads but this heads has 2.15 intake valves and I believe that 4.000" bore is not enough for a good valve shroud. This is the main reason that I'm thinking change for a 340 block, maybe use 4.080" or 4.100"