Sorry about that. I fixed the permissions on the files, you should be able to download them now.
The injectors are wired up in two banks of six, with bank 1 matching cylinder bank A and bank 2 matching cylinder bank B. The Lucas 6CU and 16CU are wired in the same manner but appear to fire both banks at the same time. Much like the Megasquirt there is only effectively one injector driver per bank in the Lucas setup, the two groups of three injectors on each bank are run to the same pair of transistors (one peak, one hold) inside the original ECU. I believe the only stock EFI setup on the XJ-S to do alternating batch fire was the Bosch D-Jetronic on the non-HE engine and it still fired 6 at a time, three on cylinder bank A and three on cylinder bank B.
The stock injector resistor block has four resistors, one for each group of three injectors. If you look at the rather confusing wiring diagram Lucas saw fit to inflict upon us, you can see that the A bank injector hold resistors are wired to pins 12 and 30 on the Lucas ECU and the B bank injector hold resistors are wired to pins 11 and 29. The pins for each bank are tied together internally and are routed to the collector on the hold transistor. I simply neglected to hook these up to anything as the Megasquirt only has one transistor per bank, the only thing I connected were the "on" injector pins, namely 13, 14, 31, 31 for bank A and 8, 9, 27, 28 for bank B. I left the original wiring to the injector resistor pack in place in case I need to plug the original ECU back in.
The timing signal is currently coming from the stock ignition module heading back to the original ECU (pin 18.) The 7-pin HEI module in the photo you referenced:
http://crosstalk.atomz.com/~ross/jagstu ... 046037.jpg
is to allow the Megasquirt to control ignition timing using the stock distributor VR pickup. I modified a junk CEI distributor to lock out the mechanical advance and removed the vacuum advance can. I then modified the VR sensor mounting plate to allow me to lock it in an arbitrary position (basically added a setscrew that holds it in place.) This makes the distributor rotor position adjustable so that in the base timing position (about 8 degrees advance) the trailing edge of the rotor tip can be just passing the contact on the distributor cap to give the maximum range possible for ignition advance. I haven't tried installing it yet, but if Easter weekend turns out to be quiet I may have a chance to give it a go. Ideally I'd like to install a crank trigger and do away with the distributor entirely, but this does allow for a limp-home mode if I had to use the original ECU. I'll take some photos before I install it, and let everyone know if it actually works.
The wiring block bolted to the bottom of the gutted 6CU case was just something I had lying around, I don't think DIY AutoTune sells them. Here's something very similar from Digikey:
http://search.digikey.com/scripts/DkSea ... =CBB112-ND
Hope this helps!