2008 DHRA Rule Book Amendment –Page 26- Sled Pulling Section – Super Modified – Engine

The engine block must have been available as a factory option or a replica of a factory block from a one-ton or smaller pick-up truck. The following criteria(s) must be met when a replica block is being used: Replicas must maintain the original cylinder head bolt pattern, original cam and crank shaft positions and original exterior block dimensions. The block must be able to accept the stock crankshaft. A harmonic balancer meeting SFI Spec 18.1 is mandatory.