Streetjammer
A streetjammer is a carriage or wagon with a streetjamming helm attached. The most distinctive feature of any streetjammer is the guidance mechanism attached to the helm. This may be a simple steering wheel similar to those found on modern vehicles, it may be more similar to a ship's wheel, or it might be a stick or even, in older models, a set of reigns and levers designed to accommodate a driver more used to steering a pair of horses.
        Streetjammer: Helm: streetjammer; SZ: Large; Face: 10 ft. by 10 ft.; Crew 1/5 (untrained/+0); Mtl: Wood (5); hp: 3d10 (average 16); Init: -2; Spd: 80 (good, land only); AC 9 (-1 size); Atck: None; SA: bludgeoning; SQ: None; LC: Land; Cargo: 1/2.

Helm, Streetjammer: The standard streetjammer helm takes the form of a padded leather chair with footpedals and a guidance control (a wheel, a stick, or other mechanism). When installed on a carriage or wagon, the streetjammer helm grants that conveyance the ability to move under its own power, with a base speed of 80 ft. The streetjammer helm may be operated by anyone seated upon it.

Caster Level: 6th; Prerequisites: Craft Wondrous Item, haste; Market Price: 10,000 gp; Weight: 250 lbs.

I had no idea how to determine the caster level, prerequisites, market price, or weight of this item, so this is almost entirely guesswork based on the same stats for spelljammer helms . . . suggestions?