I ran across a 1989 300zx with a locked up engine, needs a new engine. The interior is beat up a bit.. things held together with duck tape. The outside is beat up some, some rust etc.

What should I pay for the car?

Sounds like nothing more than a parts car to me, so I'd offer $500. I'm sure if you look around, you'll find running examples for a far better price than what you'd have in this one, should you decide to get it, source and install a new engine, and fix everything else...

Interesting, I was thinking the exact same amount.

I think was zbane means is don't buy it. I wouldn't unless I already had one and needed a parts car. Those are somewhat pricey to work on and you could buy a fairly clean running one for less than you'd invest in this one to get it to that point. About 6 years ago, I bought a running 86 300ZX for $1200, did brakes and a starter and sold it for $2K 3 months later.

If I had the car you described for free or a running/driving car for $1500, I'd pay the $. An abused car like that will have a ton of problems, that may take you 100's of hours to fix and thousands of dollars to sort out.

The nice thing about these cars is that they made a ton of them. You can find good examples for cheap very regularly.

I agree with everyone else. Buy it for a parts car after you buy one that is running and driveable.