Headlamp bulb types?

[Joolstacho]

Is anyone 'across' the intricacies of Lucas bulb (globe) types/fittings? I'm working with BPF type base.
I recently bought an LED hi/low bulb/globe (which is super-bright I might add) But... I had to do a slight adaptation to it because the distance between the flange plate (with the little semi-circle cutout) and the contacts is about 2.5mm shorter than the old conventional bulb I have. The LED was listed online as a P36d,  I have a reference listing a P22d (P36d). The older conventional bulbs I have measure 16.7mm between flange plate and contacts, but the LED globe measures only 13.25 - so it's a shorter base.

I've got around it by putting a 2mm thick copper washer ring underneath the flange, which moves the globe upwards to reach the contacts.
But I wouldn't mind getting to the bottom of this, E.g, what's the number in brackets?

The ebay seller has hundreds of LED bulbs,  lists a P36d and P15d but not a P22d. It was very cheap, but it's good (I even managed to drop it on the concrete floor without hurting it)

Any clues?

[KiwiGF]

Is anyone 'across' the intricacies of Lucas bulb (globe) types/fittings? I'm working with BPF type base.
I recently bought an LED hi/low bulb/globe (which is super-bright I might add) But... I had to do a slight adaptation to it because the distance between the flange plate (with the little semi-circle cutout) and the contacts is about 2.5mm shorter than the old conventional bulb I have. The LED was listed online as a P36d,  I have a reference listing a P22d (P36d). The older conventional bulbs I have measure 16.7mm between flange plate and contacts, but the LED globe measures only 13.25 - so it's a shorter base.

I've got around it by putting a 2mm thick copper washer ring underneath the flange, which moves the globe upwards to reach the contacts.
But I wouldn't mind getting to the bottom of this, E.g, what's the number in brackets?

The ebay seller has hundreds of LED bulbs,  lists a P36d and P15d but not a P22d. It was very cheap, but it's good (I even managed to drop it on the concrete floor without hurting it)

Any clues?

Vaguely related….a mate (long story) left his A10 in my shed for months and when he picked it up a couple of days ago the battery was virtually flat, and his LED headlight didnt work even with the engine running…..rear light did  it turns out he had installed a 12v LED headlight bulb in a 6v system ON PURPOSE as he found the 12v LED would (just) work perfectly when the battery was near fully charged. Sure enough after a couple of mins of running the headlight started flickering on (I guess in time with the regulator) and then stayed on.

The point is, 12v bulbs are cheaper and more readily available and may very well work fine on a 6v system.

I don’t know if he had a std reflector/ bulb mounting, I know he had tried halogens without success as they took too much current and drained the battery on long runs.

[Joolstacho]

I've got no probs with the LED bulb, -Cheap, very bright. -Just the fit of the BPF base is the issue.

[KiwiGF]

Some info here

https://mgaguru.com/mgtech/books/pdf/Lucas_bulbs.pdf

[Joolstacho]

Thanks mate that's pretty thorough reference.
Unfortunately it doesn't mention the measurement I'm after. That distance between the circular flange plate and the contacts. It's presumably a P36d LLB 326.