3CII original headlight bulbs

[Billy26F5]

Hi all,
I've been a bit puzzled by the specifications for the headlight bulbs (which are BPF dual filament DC bulbs), as the manual says they're 36/36W but the JCB parts website says it's the now very common 50/40W (bulb no. 414). Julian Carder said in the Haynes book that the headlights and worklights were Lumax made, but I can't find any bulb in their catalogue that fits the spec in the manual. The closest I could find were 6V bulbs, followed by the 42/36W bulbs (nos. 354 and 355). Anyone have any information that makes any real sense about this?
Mr MacGregor had a Unipart 50/40W (no. 414) and a modern repro 50/40W that he got when we got him, he now has two 42/36W bulbs (no. 354, one is an Osram GEC, the other a Florida). We also have 3 Lumax 50/40W (no. 414) awaiting use, but as I wasn't sure I decided to use the less powerful bulbs for now. His worklights are unfortunately some aftermarket type, so they're not in the same doubtful situation.
The worklights use the 48W CC BPF (no. 185) and there's little doubt about them (I think, although it could be a slightly different bulb such as no. 323).
Any ideas are very welcome.
Sandy