engine and plugs

[chaz]

afternoon all. finally got round to firing the old girl up....
just after a bit of clarification.
frame number ZA7530329. me thinks it should be ZA7S 30329
engine number shown as ZA102933, CI head and barrels.
my thinking is its a 1952 plunger engine possibly in plunger frame but numbers are off the last 2 V5s not sure if its original despatch must get round to renewing membership.
BUT
can some learned person let me know what plugs to use?
NGK as Champion are harder to get. Are the B6HS in atthe moment OK LHS is missing at moment.
thanks

[Brian]

Chaz you have a 1950 engine and a 1952 frame.

Either B6HS or B7HS will be fine.

[chaz]

Thanks Brian, originally told it was a 54 engine in a 52 frame best to make sure. Roy Bacon;s restoring book only gives starting numbersp