Super Stock wheel arches.

MOPARMAGA said
Ooh, then I might reconsider welding a plate in front of my inboard spring boxes

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Yeah the 29.5 X 11.5W can be anywhere from 30” to 31”. My last set were 30.6”. They fit at the front but there’s approx 3/4” space. A second bolt hole on either the spring box or spring perch will give the room needed.