Without a doubt you will have to change heads,cam,and have a superior valve train to turn 6500rpms not alone 7500! Block durability is a major concern above 6500. It will not hold up! Your "all forged" internals will be worthless in a stock block. If you're going to turn high speeds you'll need a solid roller cam and probably a shaft mount rocker system. You also will need a lot of ignition upgrades. With a high end head,studs,valvetrain,etc you're talking about 4000$ in parts to run anywhere close to that rpm level. You also need an aftermarket block which is about 2-2.5k. The engine you are describing is about 12k-15k not 8! A good stock block build still needs heads,cam,etc and can produce close to 500hp but will be limited to around 6500. Hyd roller cams tend to have valve float around 62-6500.