Dany's race car adventure, or help us spend my last $1500 wisely!!

Gears and wider tires first.
Your biggest up coming issue is your torque converter because of the spline count.

I had my wife’s ‘67 - 18 spline count converter modified here: ProTorque High Performance Drag Racing Torque Converters

Worth every cent! Save some money up for this.

You can make due with exhaust manifolds for now. Even if you have to cobble up home made dual exhaust, do that. H pipe it.