Gentlemen,
Lister, since the begining of time, looked at oil pressure for what it needed to be... not what most thought it should be and accordingly, 7psi was common for nearly every engine they built (turbocharged engines are the exception) so no matter what or which filter you use, it's not like you can hurt anything within the engine. Also, cloned Listers are exactly that... they don't need hybrid anything!With the exception of the JAS, HRS and several of the S series 4 cylinders, nearly everything Lister made incorporated a jerk pump (a piston acting on a lobe on the cam) installed on 1,2, and 3 cylinder engines. Sounds strange? Not really as every Lister had such generous main and rod journals. As per the Engineers: Keep the journals wet enough to lubricate and toss oil onto the cylinder walls. It's also an oil consumption control device. Honestly, the journals need not be flooded as the journals are large, capable of far more BMEP than these engines are capable of. They simply don't need to dissapate excessive amounts of heat. Add to it, the babbit overlay, high pressure oil can do more damage than good. At any rate, and these engines were designed to run at least 20,000 hours so please don't worry about oiling issues... Synthetics aren't necessary as the clones aren't of the quality Lister manufactured however oils such as Rotella Valvoline Cummins, etc would serve the purpose well.
If you're installing an oil filter, use an extremely heavy copper tube (not air conditioner tubing) as per the HR range of engines. If you're installing a remote filter use hyd. hose... it's your investement... besides, wouldn't you prefer sleeping well at night instead of worrying whether or nor not a tube is going to crack?
Bill