Glen-
Do you plan to make your car right-hand drive (requires custom-made footboxes, according to the ERA site)? If so, there is more room to the right side of the center, dropped portion:
The story behind this curious arrangement is that, being British, the AC cars were nearly all built right-hand drive (other than the relatively few that were exported), so the dash was cut to provide more leg room on the driver side. When AC built cars that were left-hand drive, AC did not trouble to flip the dash template, so the dropped portion of the dash wound up encroaching on the driver's right knee! Jim Holden pointed this out to me.
Jeff