[bmw5002]

I am looking into a suspension kit from mustang depot for my 65 coupe that comes with 600# front coil springs. I don't know much about mustang suspension but I know that with my WRX, anything over 250# is starting to get stiff, and over 300# of spring is pretty damn stiff. So I cant imagine what 600# of spring is like, maybe like having no suspension at all? Those springs are the only option in that kit. What is a normal performance/occasional track driving spring rate?

[5.0 in a 66]

WRXs use struts whereas Mustangs use what's called an SLA system (Short Long Arm) with traditional coil springs and shocks, like what you'd find on the front end of a 93 2WD Cheby. Mac-Strut and SLA systems are different beasts.

That said, 620s will still beat your brains out and so will KYB Gas-A-Just shocks. Combine those and you just might punch a hole in the headliner with your head when you hit the first bump.

I'd look at KYB GR2s and 480-550# springs. I'd investigate a whole kit from John at OpenTracker Racing. He inspects and tweaks all his new control arms and the prices aren't a whole lot more than the competition.
HTH
--Kyle