Omega 6 cyl engines are V6 not straight 6
I did prefer the older Senator which had a straight 6.
I've converted them with spare wheel tanks and with cylindrical tanks. A cylinder tank mounted in the boot will of course always take up boot space, spare wheel tanks don't need to take up any boot space but it's possible to fit a taller spare wheel tank (that rises above boot floor level so takes up a bit of boot space) - You choose the compromise.
Won't need a lube.
You probably haven't looked how/where to route injector pipes on the V6 yet - You'll at least be removing the upper manifold to fit normal spuds (access to correct location). When fitting spuds make sure they're not in a location that will pinch injector pipes when the upper manifold is refitted
...there isn't much clearance between the lower and upper manifold to route injector pipes without pinching them even when this is considered. Obviously if an injector pipe is pinched it will lead to problems with misfire/lean fuelling to the affected cylinder - Small diameter (4mm ID) injector pipes are a good idea for this engine for an amateur (easier to route without pinching) but would rule out most injectors (that have outlets to suit 6mm ID pipe injector pipe)...
I have sorted loads of Omega's with pinched injector pipes. One comes to mind where the owner had had his car converted 5 years ago but it had always run poorly under heavy engine load... Over those years he had re-visited the original installer many times, taken the car to a few other installers and even taken the car to the LPG equipment supplier, none of them correctly identified the problem but he'd paid them for diagnostics, new plugs, coil packs and several sets of LPG injectors. The same has happened with MG V6's.
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