Andrew asks:
Not strictly steam I know, but do you know what engines were fitted by McLaren to the Fowler ploughing engines when they converted them to diesel engine? I believe they were of McLaren manufacture.
To complete our answer our expert Peter Longfoot reports that McLaren used their own engines for these conversions.
The BB1s were converted with 6 cylinder MDB6 engines.
The K7s used the 4 cylinder MDB4 engines. He thinks only one pair of K7s were converted by McLaren.