Simon,
Thanks for posting your solution. This sounds ideal as proprietary funny car air springs are not up to the springing/damping quality that a 40 needs. And it is near impossible to install a passive air spring in parrallel with the main coil over unit, such that it only comes into play when pumped with air to raise the front (impossible due to space restrictions in the suspension). With the long front overhang, even one inch would make quite a difference. Ideally two would be good, but no good if the spring is then too short and stiff to handle bumps at high speed.
The air pumps, switches, even air tanks, are readily available here (Sydney, Australia), but is the spacer "piston" unit something you fabricated up?
Regards,
Dalton