Asking price seems reasonable, but I have paid less for better condition 320s (before you figure in shipping/transmission). I recommend doing some quick "get it on the road math" for parts and make an offer.
I caution on the "just need to bleed the brakes" line. These are old little trucks with polished aluminum lined wheel cylinders, brake and clutch master cylinders - i.e. the score easy. Kits are available on eBay, just have to look, and all brake and hydraulic items are available from your local parts store, but this will cost you up to $500 if not more if you do a complete rebuild, which I highly recommend.
So again I'd figure in some numbers and make an offer around $1200 and compromise at $1400.
Wayno hit on the rust, and from what I see the rocker and behind the seat look to be the worse - rust repair can get expensive, is not guaranteed, and you will be paying even more for fabricated panels that probably will not match very well.
As Wayno pointed out 320s do not seem to be selling - One is because someone asks an outrageous price for a 320 with a missing motor, front glass, doesn't run, or desert/barn find missing lots of bits. Tried to sell my one '65 and got just one bid - and I was not asking something stupid. Oh well, it's still my daily driver and it helps out the neighborhood for all sorts of things.
Carburetor looks to be from an A Series Datsun engine but not too sure of this.
All mechanical parts are available or can be had. The exception is the transmission gears. You said it goes into first, so the first (no synchro) and second gear sychro cluster should be good. If you have to use gorilla strength to get it in first gear the synchro is bad, I recommend walking away at this price. There are no internal replacement parts available and a transmission swap is your only and expensive option.
Here's the link to my flickr account if you would like to take a look the different rebuilds and pics for reference.-
https://www.flickr.com/photos/113742723@N07/albums
Any questions just ask
Good luck,
Li'l Truckie