The GWR Exchange Station was roughly where the FR/National Rail station is now located in Blaenau Ffestiniog. The GWR called it simply 'Blaenau Festiniog' (spelt thus) but under BR it was renamed 'Blaenau Ffestiniog Central' to distinguish it from the ex-LNWR station (and to correct the spelling). In FR timetables it appeared as 'Blaenau Festiniog (GWR)'.
Dolgarreg ddu, the location of this station, was originally the western terminus, and junction with the FR, of the Festiniog and Blaenau Railway which had been taken over by the Bala & Festiniog Railway (a puppet of the GWR) prior to gauge conversion in 1883.
Following the gauge conversion there was cross-platform interchange between the FR Co. and GWR, with the standard gauge running where the FR platform now lies, and the FR track running in the area where the Network Rail lines are, continuing across the present-day car park and then onwards under the road bridge (now removed) to Duffws station close by.
On the south side there was a large yard and goods shed for transhipment between GWR and FR.
The BR line to Bala eventually closed in 1961 and the line was permanently severed towards Bala by the creation of the Llyn Celyn reservoir in 1965.
However, in 1964, as part of arrangements for access to Trawsfynydd nuclear power station, and with agreement of the new FR Co. management, the remaining former GWR line to Trawsfynydd was joined to the former LNWR line to Llandudno and the national network, using the original FR Co. trackbed through Blaenau Ffestiniog.