Tony,
If you're only going top model one of the level crossings, surely, you only want the pannier tanks working in the area?
During 1955/6 the following pannier tanks were at Croes Newydd:- 1635 1646 1660 4617 4645 4683 5416 5742 5774 6404 6405 6422 7403 7409 7414 7433 7440 7442 7443 7447 9669 9793
You haven't stated what gauge you'll be using.
The proposal of a crossing has little operational interest. Have you thought of modelling Coedpoeth; 'not big, but has a run-round function, plus passenger possibilities. I could give you an 0-gauge scale drawing of the building, for laser cutting.
I've an 0-gauge scaae model of Rhostyllen Station, laser-cut from a drawing. However, whilst the platforms are of a reduced scale length, extra trackwork has been incorporated for greater operational possibilities.
There were two SLS Specials on the branch; the first on 06/09/1952 was a joint venture with the MLS, whereas the second on the 18/08/1959 was solely an SLS Railtour. There was an REC special later (img715), but I've a feeling it only went to Brymbo. See the third picture taken at Wrexham Exchange; whilst I took the picture, I couldn't afford the fare.
I've many photographs in/around Brymbo in 1965, but they largely feature the heavier freight locomotives.
I'm from The Rhos, and left the area on St. David's Day 1975.
If you 'phone me on 0161 439 4849 I may be of more help to you.
In the meantime, hopefully, there's a picture (img692) of a freight approaching the turn-back to the steelworks at Brymbo Middle Box, sometime in 1965....I'd have to look it up! And, not forgetting the banker (img693)! Due to my lack of familiarity with this site, I deleted img692, and had to reinstate it. Hence it being in the wrong order.
Peter Prydderch