First off, welcome to the forum. If sled is a 1998 670 MXZ, it's not a HO and has around 110-115 hp. If sled is a 1999 670 MXZ, it is a HO and has around 125 hp. Manufacture date of 1998 would make a 1999 sled. Either one is in the s-chassis, but the 98 would have standard DSA front suspension, while the 99 would have DSA plus.