Typical sized cars heres the formula ( yours would be worse)
Top speed (mph) 20 times cube root of horsepower
Example 400hp cube root is 7.36; times 20 is 147 mph
the hp climbs exponentially much high the faster you go aka drag limted
So your magic 340 was making what 550 600 hp @ 6900 with stock valvetrain gotcha
rusty would need about 700hp no problem with his magic low comp 340 at 4000 lbs