Go with a windstar upper manifold. Just that alone gives 7hp and 15lbs torque to the wheels. Acceleration you want an LSD and rear gears like 3.73 or 4.10s if you don't care about fuel mileage. If you want more power after that, like previously said rotational mass is just free horsepower. Aluminum driveshaft and smaller aluminum wheels will make you feel faster. If you're serious about more power after that, go for new head and a centrifugal supercharger. Easily add more than 200 HP to the wheels with both those mods
65 Mustang coupe
306 H/C/I, holley 4 barrel, T5, Hurst Shifter, Subframe connectors, 8.8 w/ 3.55 posi, 4 piston front disc brakes, SN95 rear disc brakes, shelby drop, 620 springs, Mideye 4.5 Leaf Springs, bilstein shocks.