1964 1/2 worth? and restromod

ok, my dad has a 1964 1/2 mustang Convertible, 289 D code. the last digits of the VIN are 7021, that has sumthing to do with wut number it is made right? it is an Automatic tranny. so we would like to know about how much it is worth, it is mostly 100% original! minus the carb,intake, and paint,

it has a diffrent carb and intake and it has been repainted alongtime ago, factory color. it has 69K miles on it. we have ownd it for 25 years. we are the 3rd owner of it. most EVERYTHING is good condition. the body has very few flaws. just minor. it was built in san jose, and staid there for along time till my dad bought it 25 years ago, it is in MN now.

it runs and drives, needs alil brake fixing and carb tuning but it runs!

any idea wut it is worth?

my dad either wants to rebuild the motor hop it up and drop a T5 behind it, or drop a 93-95 5.0 gt or cobra motor in to it with a T5. or just sell it. what are all your opinions!? thanks!