I'm looking for suitable track and trains for WW2 Burma a bridge too would be handy
I know nothing about locamotives or even the gauge of track they would have used
Burma used 1000mm (1 metre) gauge, therefore "00" gauge model track (which is the scale name for 16.5mm wide gauge 1/76th scale track, but actually 1/87th scale, because it's identical to "H0" gauge model track) would be a little too wide to be in scale, but would do for wargaming. If you want to show the weak track in Burma (and given that it's available wherever in the world you are) you could look for PECO 0n3 track, which has wider spaces between the sleepers. There is also H0m with 12mm gauge which is continental European 1/87th scale 1000mm narrow gauge.
In 1942 the country had 3.313 km of metre gauge track, but by the end of the war only 1.085 km were operational in four isolated sections.
I can't tell how particular steam engines in Burma have looked at the time, but I think those were small engines (maximum 12.5t axle weight in Burma). A four axle-engine must have weighed no more than 50 tons, which is fairly small. I found a picture of a large engine which is an articulated Mallet to bring power to the steep gradients and curves:
https://www.irfca.org/gallery/Heritage/internet-archive/burma-mallet-1916.jpg.htmlI have something similar by Bachmann for colonial wargaming in 28mm:
There were thousands of bridges and the famous River-Kwai-Bridge was one of them.