We can make them a bit wider here, width is limited dependent upon class however. In the Prepared classes I believe all are set at a maximum of 38 inches wide. Unaltered wheelbase in reference there, is measured from center of front axle to center of rear axle at the hub. The distance should remain the same as originally designed. Essentially you can't shorten or lengthen the frame.
Likewise, we have to use a lawn tractor seat. No high backed cart style seat like you guys are allowed there.
And, we are required to run a factory deck in all but the Factory Experimental class. We are allowed to piece the deck and mount what are commonly referred to as "deck halves" to the running boards. Most also cut the deck down to a height of 1 1/2 - 2 inches to allow for clearance, since there are mandated clearances for both deck and frame.
Likewise, in the FX class you are required to fabricate something that resembles a deck in design of your running boards. Your machine with the fabricated chassis and running boards/deck would very likely fall within the rules for FX class, dependent upon engine size. There we're limited to a 465CC engine.
Copy of the 2007 USLMRA Rules is found here on the forum...
http://www.heymow.com/index.php/topic,1538.0.html
