[Brian]

Pooch, All Pilot engines originally ran flanged on one side, lock in shells. The crank journals have double oil holes accordingly, however, the holes are on opposite sides of journal to each other. These bearings are very hard to source nowadays, however, 32-38 USA flanged full floaters will directly interchange quite happily.
Apart from the double drilled rod journals, Pilot cranks have the longer /larger diameter snout, same dimensions as USA post 38 cranks. In all other respects the Pilot cranks resemble 36LB-38 cranks.
The Pilot blocks are a different casting to USA 37-38 blox; behind each bank of cylinders [behind #4 and behind #8] they have a 5/8" dia frost plug [English terminology], which makes them easy to id.
So...when your Thames engine arrives, first things to check are to see if it has the frost plugs as described, also if it has the long crank snout, if so, it will be identical to Pilot.

In my adventures with 21 stud blocks, I have found yet another English variant; wartime military use, eg brengun carriers, These babies have no freeze plugs anywhere [not even in the panrails], have what is referred to as 'raised deck', and have the third hole at back of block for oil cooler. These are cast in what appears to be a very high nickel iron; the water jackets don't demonstrate any tendency to rust/scale up. These blocks however, in my experience, can crack in all sorts of places. I have previously been caught out with this variant; initially one thinks, by virtue of the clean water jackets etc,that they've got such a pristine block, only to have ongoing problems with cracks forming.

I hope for your sake, that your engine turns out to be a Pilot version. Good luck!