Here's my old sled '02 Summit(RIP) it was a 144:
That millennium sled is a 136 it would say. If memory serves me correctly mine had a small extension piece right on the rear of the tunnel where I have the gas can. 151 tunnels had the small piece but it was twice as long. 136 tunnel has no extension piece. But on the other hand we are talking about track length not tunnel length
my dad has the exact same sled. i love the 's' chasis, they are amazing to ride. one of the best sleds bombardier made, i think the rev platform sucks for visuals. the 97 - 03summit line up is my favorite type of sled by far to any other.