Not sure if Landi (system) took over from the LandiRenzo systems, they're very different though.
Over the years Landi Renzo did make some unusual systems, though as Gilbert said some are compatible with the generic AEB stuff.... But don't presume just because a generic AEB type ECU (AEB2568) would fit the connector for a Landi Renzo system that it will be compatible - some may fit but use a different pinout on the connector.
There are a few very different AG systems... Some are compatible with different injectors etc, some are real oddball systems that a separate ECU / injector emulator. The latter (also known as Teleflex) you can't even calibrate because the ECUs were either mapped at the factory or the installer downloaded a map direct from AG and the maps are no longer downloadable, no manual mapping options in the ECUs at all. I have an interface and software but it's only really useful for checking pressures (or rather confirming suspicions of a broken pressure sensor). I have a few second hand spares for them including injector emulators, sensors, injectors etc, (no point fitting an ECU unless it came out of the same model car) but I wouldn't even advise playing with one that seems to be broke unless it's something very simple like a fuse lol.
Autogas2000 in Thirsk are a distributor for Landi but not for LandiRenzo. They were never great at installing but used to have decent and helpful staff (for their trade customers when they were a bigger supplier, as well as for their conversion customers)... but they seem to have gone downhill - This year I've converted over 20 Nissan Elgrands, they converted a few before me but made a real balls of them. Some of their customers took their cars back many times but all they did was plug the software in and change a few numbers in the map, eventually fobbing the customers off with a massively compromised install. I had the software for Landi but didn't realise a new version had come out in April2016 or that newer ECUs running newer firmware needed the newer software... They gave me the newer software (seemingly grudgingly) and I went on to sort out the problems on cars they'd converted... cars that basically were almost undriveable on LPG until I sorted them. So bad that is was probably just as well that they'd set them up to switch back to petrol at high loads and even switch back to petrol below 1300rpm because they were incapable of even idling properly on LPG!. One guy used to switch his car back to petrol for town driving or the engine would surge in rpm massively as it continuously switched between petrol and LPG at around 1300rpm when he was setting off (or particularly when reversing). All running nice and smoothly without using any petrol after I'd fettled them ;-) Not just a calibration problem though, they'd fitted massively undersized nozzles and the Landi reducer isn't adjustable away from 0.9 bar. Even after I'd fettled them they're still compromised a bit because of the long pipe runs they'd used and even with the bigger nozzles I drilled out the injectors won't flow enough to run totally on gas flat out high rpm - I could have sorted all the problems but customers wanted to keep costs to a minimum.. can't polish a turf.
From what was said they all started from the same company, and some sort of disagreement ended up forming Landi and Landi Renzo. So the early stuff is all the same, the later Landi and Landi Renzo may be similar but certainly not the same.
At any rate, if its a Landi Renzo he has got, its likely to be well past its best by now (look at mine that constantly sees lambda voltage of .38 even though the wire isn't connected to anything now), and given the limited choice of injectors natively supported it would be more sensible to ditch the ecu and go for a new one, giving far more choice of injectors?
You can try to polish, but you end up covered in it!