Note that really narrow gauge track can support large loading gauges, like the ex-73 class locos on 610mm cane tramways.Loading gauge has little to do with track gauge.
Wilmar has been busy rebuilding three of its 40-tonne ex-Walkers B-B Diesel Hyraulics (from a fleet of QR DHs, NSWGR 73 and WAGR M) for this season - bringing to a total of eighteen $1.7 to $1.8-million rebuilds in what is a 10-year project to upgrade its biggest locomotives to reduce fuel consumption and emissions. Work has been carried out at Wilmar's Burdekin Workshop - its centralised locomotive rebuild centre located at the Pioneer Mill near Brandon. Four locomotives were rebuilt in 2021. The project includes new cabs, primemovers, cooling modules and transmissions using only the frames and bogies from the donor cores.How dare Wilmar be considering building their own locomotives in-house. Don't they know that not making extensive use of contractors is the road to economic doom. And anyway, the previous NSW Premier said we're not good at building trains in Australia.
With only a few more ex-Walkers B-B cores available, Wilmar is now shifting to building entirely new locomotives (including frames) as it continues to upgrade its fleet.