Greg's rear IRS looks the same as the original IRS I saw back in 1995 or so when it was ACI, which Greg got the molds/jigs for and started Vintage Spyders.
I don't know how many IRS rears have been done but I think not that many in 25 years. I've only seen maybe one handful in pictures, but I'd guess less than 1 a year.
As far as the rack and pinion steering, I'll let you know. I have all the parts to convert mine, waiting for the rain to rinse the roads clean of salt. Then the Spyder can take the prime "work" spot in the garage.
@aircooled I wasn't aware that rack and pinion steering was commonplace in Spyders. Is it really?
@550 Phil The steering box isn't the best, but properly adjusted it isn't bad. But hey, they RACE Formula Vee with them, they're required.
The front suspension issues are all packaging: brake/clutch masters, foot room, gas tank room, and get a good unequal-length A-arm in there with good Ackerman, no bump steer, and yeah some room for the steering column and rack too. It's a lot to package in a small space. I hope it can be done without lengthening the wheelbase.