It's hard to assess just by looking at the pictures. Rarity is not an issue to consider, really they are both in the same category more or less. You don't have the money for a 350 but here you can have one for free -- so it might be a worth while option, but you just want to make sure you don't get screwed, right?
Things to consider:
Why does he want to trade? Is he tired of paying a lot for gas? Or is the engine on the way out, or maybe the frame rails are rotted, or maybe it rattles too much or the windows are too loose or there is no heat and the AC is shot, who knows, but you need to find out the real reason.
Things to do:
Thoroughly inspect his car, open the trunk and look under the carpet and spare tire areas, and inspect the brake and signal light wiring etc. Look under the car, specifically the frame, and especially the rear frame rails, inspect for rust and rot. Look at the interior, lift the carpets up and look at the floor pans, are there any holes/rust?
Drive the car, feel the shocks, handling, steering compared to yours. Check that ALL the accessories, switches work.
Lastly, find out about that 350. It's obviously aftermarket. What's the mileage on it? How is the fuel consumption? How does it start (every time), idle, and rev. Smell any burnt oil? Hear any noises, ticking, etc? How hot does it get?
Get a compression test on the cylinders.
If the car is really comparable to yours and the engine checks out, and IF you won't mind paying extra for gas in exchange for the extra torque (to me, it is well worth it), then I say GO FOR IT! Just be careful, take your time and do those things ^^^ and you're golden. :wink: