Well, I have made a lot more progress on this. Software testing is almost done, and I have ironed out a LOT of bugs. This thing is starting to be really solid. I have been delayed by nuisances like having to tear my M42 down thanks to a dead timing chain idler sprocket, troubleshooting a bad ground on my wide-band O2 sensor setup and trying to convince my fiancee that she is at least as important as my car projects.
Anyway, I expect to be designing & ordering some debug PCBs in the next couple weeks so I can really iron the last details out. From there, it is just working out the converter's packaging & cabling. I know this has been a long time coming, but it should be well-worth the wait.