Gresley-4498

Loco comparison is interesting, I think it's the wrong wagon to compare as the dimensions will be largely dictated by the size of the shipping containers. (but as you note, it's the one you have)

Hornby have acknowledged a number of manufacturing issues with the A3/A4 and have provided some advice on resolving them, including adjustments to make them work better with Peco track, for example. There is a thread here outlining the common fixes: https://community.hornbyhobbies.com/topic/33745-the-main-a1a3a4-chassis-bogie-problems-fixes/#comment-373922 Yo can also get Hornby to make adjustments for you iirc,

I'd forgotten that they'd done a J15 at all actually - in that case it's probably even odds.

I think the J36 is more likely as they would have recent-ish (2018?) cad and analysis for it, but you can dream...

73s have a lot of livery options and synergies with what has been produced so far including Pullman livery, Caledonian Sleeper (with mk3s), gatwick express (mk2s) Network south east along with all the others. Similar story for 67s as these can also be produced in Pulman, Caledonian sleeper, Royal train (mk3s), Belmond Royal Scotsman, Silver & Diamond Jubilees, EWS. DBS Colas, Arriva etc.