OPPS! Wait a sec, they call that stuff "rain"!

Not too much of that in Arizona. But we've been catching up lately. I noticed a leak in my cab on the driver's side down the kick panel. Any ideas on where to look for the culprit?
Thanks in advance!
__________________

69 C-10 LWB, 350, 700r4, 3.73 posi-traction, front disc brakes. Built for the desert-
She can take the heat! Vivat Rex Chevus!