David,
The D14 & D15 rebuilds tended to have the most recent LNER boiler mountings - backhead clacks, steam manifold, sliding firehole door, etc, and most were given the Gresley single anti-vacuum (snifting) valve, though initially boilers had the old GER pattern header with twin valves, some of which lasted until the 50s.
Of the H88 rebuilds (those which retained the valences), the first 30 retained the twin GE valves and 21-element superheater, but those boilers built after 1936 gained the single Gresley valve.
Looks smashing.