MKIII Headlamp Bulb Size?

I've read several hundred lines reference to LED Headlamps. Seen a lot of comments/discussion concerning changing to H4 bulb size for ease of finding LED options. I have also seen pictures of LEDs that will fit a stock configuration. What I have not found is what is the stock size for the MKIII reflector?
I find shopping less frustrating when I know the size I am trying to fit'

Thanks
Chuck

Saber13 said:

What I have not found is what is the stock size for the MKIII reflector?

Click to expand...

According to both the Mk3 manual and parts book the original US bulb was a 'BPF' (British Pre-Focus) 370 (P36d).

https://www.feked.com/bulb-headlight-12v-50-40w-bpf-p36d-370.html

Thank you!