If yours is clean and running well, I think he will need to sweeten the deal with some cash.

You need to figure out what you feel your '82 is worth, what it will cost you to get the '85 Runner to the level of your '82, and see what the KBB is on the 300Z if you are going to sell it. Off the top I would think your rig could bring about $5k here in CA. I know you probably have more into it, but you can't get much more than double stock value, even when built with all of the goodies.

You might also consider buying the Runner from him, I would think $5-600(no higher than $800) would be a fair price from the sounds of it.