You'll find some engineers may be lenient if you started the engineering process prior to ADR 3/03 taking effect (July 2011?). I know this is true in at least one case.
I just got off the phone to the guys selling these cheap alternatives.
SAAS Black Mach II Fixed Back Race Car Seat ADR Approved - Motorsport Essentials Pty Ltd
The paperwork is for ADR 3/02 and after I explained the current situation he contacted the supplier to see whether they are or can be certified for ADR 3/03 and he said he'll get back to me.
For the above SAAS seats, the all important height measurement is 840mm with a 30mm cushion that is velcro'd into place. 510 wide at the base and 550 wide at the shoulder - this could be a problem for most of our kits. I'll measure mine when I get home.
Edit: absolute max width of seat base in the Harrison is 450, maybe less depending on whether seat belt mounts are in the way. How about the other kits?