[TR] NGK plugs for TR2

[Randall]

> Does anyone know if this 'new' number supersedes the old BP6HS?

The 'R' just means that the plug incorporates a resistor for RFI
suppression.  Should work exactly like the BP6HS plug otherwise.

>   I take it that the TR2 can use the same NGK BP6HS as the TR3As,
> despite the slight increase in engine performance of the 3A.

Should be fine, IMO.  But if not, a set of plugs is cheap enough that you
can experiment with one range hotter or colder.  It depends as much on your
driving style as engine performance.

-- Randall