[Shelboss]

The Jag series I front uprights have I believe 3.25" bolt spacing for the Dunlop calipers. Series II uses 3.5" bolt spacing, which works with the heavy 3 piston Jag caliper, or the Wilwood Superlite calipers. Contemporary originally offered this combination with XJ vented rotors as an upgrade. When Series II XKE stuff got expensive, they modified the XJ uprights to change the steering arm to match the XKE (in front). They also machined the front XJ 5 bolt hubs to line the rotor up with the caliper.