Edelbrock / RHS heads, or go BIG block and put it to bed!

I posted the 318 build up only to show the power that i believe you have already have in your 360 but just haven't tuned it in.

This 318 is one of my favorite builds ever.

You have more gear plus 32 more cubic inches.

Your converter is a little tight but when a properly tuned carb is set on the engine and the car hooks at the line,the stall speed (converter flash) will go to a higher rpm off the line due to more power and resistance.
You 60 foot times will be way better.

A tuned carb will also give you more horse power getting your mph up where it should be.

Your dart should be running with this cuda for sure.

I would work on why it's not going this fast first and then buy the heads after you have tuned the engine in.