,
After the old piece was removed, Blacktrax welded flat plates on to close what was left behind.The rear wheel arches and part of the rear bumper needed to be rolled and cut, to eliminate rubbing. The clearancing and flaring of the inner fender also preps for the J's Racing rear over-fenders.
There would certainly be clearance issues if this bumper and rear fender were to remain untouched. 
Another angle of the flare work performed in the rear wheel well.Finally, the Blacktrax Performance S2000 had its powertrain completely rebuilt and upgraded with a custom 2.4 liter stroker kit. Jei at Blacktrax went into great detail about all of the components upgraded with the S2000’s motor, and is quoted in the photo captions:
“Custom spec 88mm Wiseco forged pistons and a 99mm stroke from a modified K24 crankshaft. Brian Crower connecting rods, ARP studs, Cometic head gasket. The block is sleeved with Darton’s ductile iron sleeves and each cylinder is bored to its respective piston. Each piston and rod is weighed and assembled together for the best possible balance.”Because of the aggressive nature of the Toda camshafts, they actually come in contact with the rockers. To correct this issue, the rockers need to be ground in order to clear the cam lobes.
The areas where the rocker and cam lobe interfere are marked in yellow.
