All of the above, Leslie!
Serious point: it is simply not possible to accurately model the 1950-70s period without several staples. Cravens, A & 141 classes, 42ft flats, H vans and corrugated opens, and AEC railcars.
Thanks to Messrs. Murphy & IRM we now have all of these bar the AEC.
As a reminder to perhaps some of us here who have had fewer birthdays than I, the AEC cars were as integral as an 80 class in a north-based 1970/90s layout.
CIE and the GNR has large numbers of them, initially used on the sort of duties ICRs have today, but also commuter traffic.
The GNR ones would be divided between CIE and the UTA, later NIR.
They were everywhere on the present system (except the NCC, where visits were extremely few). But they also got to Clones and Enniskillen, the Derry Road, Wisht Caaark boy, and Tralee - Limerick - Sligo.