89 360 engine

Hell yes, if it's in decent shape.
Is it a runner? That will give you some clues, as in the condition of the heads... 308s are decent heads performance-wise, but are notorious for cracking between the seats- like magnum heads, sometimes the cracks don't impede their use and people just run 'em. Not advocating it, just sayin'. I've only seen 1 cracked set, and had 3 sets that were good (I've been lucky). I suspect the bad set was overheated at one point. But it isn't an uncommon thing to see.
The blocks I have seen have all been in really good shape, factory crosshatch still present in the bores; they are TBI and don't suffer cylinder wash like carbed motors.
You'll need a pass. car 360 oil pan/pickup/dipstick (your 318 pan won't fit a 360), an LA intake and carb to replace the TBI, and either a 360 balanced torque convertor or the B&M 10239 flexplate and use your current convertor. Use the pullies and accessory drives from your 318 on the 360. You can use your 318's distributor, too- the 360's is a TBI-only unit.
Edit: If it's been sitting, its value is totally in your hands. If it's stuck, I would offer him just over scrap price on it- it will be a complete unknown, and a lot of it will be replaced anyways- see above.