Sounds like an even trade, or even a little in your favor.
As you note, your rifle is merely an unused spare, and a similar rifle can even be had a little cheaper these days. Don't forget to ask if he has a holster, speed loaders, or any other accessories he might want to trade for as well.
I personally hate driving, so I'd probably pass just for that reason. Otherwise, it sounds pretty fair.
The only other thing to think about is if it's truly something you want, or if you are just biting because it popped up. Would you be happier taking a hit on trade value and putting that carbine towards a different revolver on the top of your list? Or is that M60 just the gun you've been looking for?