How Much Boost for Cast Iron Internals?

Im running 7psi on my dart with a complete stock 5.2 magnum, with 150k+ miles in it, Efi and a vortech V3 supercharger. Running low 13's all day long on 245/60 bf goodrich radials. Looking to increase boost a little and rebuild the engine soon, but will keep it stock internals. Hope to see the 11"s in the 1/4 with better tires, more boost and a set of piston rings that seal hehehe.