The Indy Drag Pak motor is a cast iron block 5.7/6.1 hemi with 6.1 heads per NHRA rules. The Barton 426 hemi is a special Mopar crate motor package developed for the NHRA Factory Stock class. It is specially machined aluminum block and Apache heads with a larger throttle body. What Ray and David Barton have done with these motors is truly amazing. They not only have the fastest Drag Pak in the land, they have the fastest Factory Stock car in the land. On a side note, a Drag Pak with a 426 Gen III hemi driven by Kevin Helms won the national championship in NHRA Stock Eliminator this year.