well according to Screamscape.com they've said that there's a rumor going around that the new ride itself will be a throwback to Knott's old popular ride "Great Soap Box Derby". This is what Screamscape said:
All eyes are on Ghost Town these days, waiting to see just might pop up for next season and I think we may have the answer. Taking a page from this year’s successful new Sierra Sidewinder, the park may opt to add another great family attraction like this in 2008. The kicker here is that this may be a throwback to a once popular but lost Knott’s Berry Farm attraction… the Great Soap Box Derby. If the latest rumors are true, a new Ghost Town horse themed steeplechase style coaster may be in development under the name “The Pony Express”. The project may extend from the Ghost Town site running towards the Bigfoot Rapids and Mystery Lodge area and back. Though keeping an eye on capacity, I’ve got to wonder if this could really be a horse themed version of the Vekoma Booster Bike coaster. Anyone know more?