You could do the LS thing and mount the coils to the valve cover bolts.
Or potentially move the filter to the frame and build a bracket to go along that side of the engine to hold them below the fuel rail. The early and late (99-02 vs 03-06) Gen III LS engines had different length plug wires so you couod pick the length you liked and use off the shelf parts.
Are you planning to use LS coils or something else?
