It seems to me, to be hard to think of 'Tru Jen' and the Masport Cup, without remembering Southward's 'Red Head'.
Certainly, Southward dominated the Masport Cup for a decade, as a fair and generous competitor.
Many of the race boats ( and cars) of that era, were built using surplus WWll materials, an area in which Len Southward ( later 'Sir' Leonard ) was very familiar. Along with Gillies and some others, Southward purchased tons and tons of surplus war materials...especially aircraft engines, which he would dismantle to recover scarce and precious metals....these providing the wherwithal to develop his first attempt at a seamless tube manufacturing machine.
The time I first met him, all of his rather random and eclectic collection of vintage ephemera was stored in an adjunct to a factory in the Petone area. he had approached the company I worked for to see if we could assist with providing or manufacturing replacement big end bearings for the GM-Allison V-1710 that resided in Red Head.
We could not, but we did look at machining the existing bearings. pinning them to the rods and then using inserts from, ISTR, a Ford Thames Trader Diesel. Finally, I believe, we signed an authorization in order that he could secure an Import Lic. to procure the correct replacements. I don't think, though, it was his intention to ever actually race Red Head again....possible he wanted to have the engine as a 'runner' for display purposes.
BTW..as I recall Bill Stevenson and/or his company, was closely associated with Slip Ray and Mystic Miss...and probably others since then.

Apologies for the digression(s)
neville Milne