the 361 has round tube profiles and external headset, possibly 1" forks... 381 has profiled tubes, integrated headset and 1 1/8th" forks... Perhaps someone else who has seen a 361 in the flesh may be able to offer more info but if the price is right I'd buy one!
What's the difference between the 381 and the 361? Might be able to pick you up a tidy 361 locally for cheap...