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Low oil pressure

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There is a reason that the factory switched from the "vane" or "rotor" style pump to the gear style. The rotor pump moved way too much volume and created a lot of back pressure on the pump driving spindle, that created a lot of back pressure on the camshaft, that put a lot of pressure on the camshaft thrust plate, that put a lot of pressure on the timing chain.
Many of us racers here in the US bought into the Denis Welch hype about using the rotor syle "high volume" pump for racing (good up to 6000 RPM according to his ads), that is nothing more than a 100-6 oil pump. The consequences were many ruined engines because the back pressure will strip the gears off the driving spindle and the camshaft. Not a pleasant scenario when you are in the middle of a race and your oil pressure goes away - not to mention all the ground up metal from the gears that are going through your motor. And that's when the oil is hot. When it is cold....with that 100-6 oil pump....you will have major issues with friction and back pressure. Stay with your 3000 gear style oil pump.
As for the initial post. I don't see any problem with your oil pressure.
 
The original 100/6 had a vane type pump and too small a gear on the camshaft to drive it, so it wore out. Austin enlarged the gear, strengthened the shaft and fitted a geared pump to the 3000 engine. The geared pump is less efficient at low RPM and kinder to the gear and shaft, but otherwise over the normal operating range produces a similar oil pressure. If it's in good condition, you can switch from a brand new geared pump to a vane one and not see much difference. A friend tried it on his, so I know it to be the case.
Therefore for normal road use I don't believe it matters which you use, but I suspect the vane type is less prone to wear in this instance. Over the years I've rebuilt a lot of engines and not often found a badly worn oil pump, but on this engine it seems to be a problem.

I don't know why vane type isn't suitable for racing engines, but they are using 7000 rpm regularly now and I doubt many road drivers spend much time over half that.
 
It's not the style of pump that is bad. For example, the 1970 era Datsun Z car oil pumps are also the vane style, but they are also quite a bit smaller than the pump in the Healey motor. They look like a minature version of the 100-6 vane style pump.
The problem with the vane pumps pushing the cam forward was so bad that Austin made modifications to the the camshaft thrust plate. At first they added a spiral groove, for oil, into one side of the thrust plate. Then they put the oil groove onto both sides so it could not be installed backwards at the factory. At some point, they made the thrust plate out of some type of bronze with oil grooves. I know this because I have examples of each. Whereas, the thrust plates in the 3000 engines are steel with no scrolling oil grooves.
 
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