Paul Willis
The High Level Kits chassis for the Dean Goods is specifically designed to have the motor in the firebox. No need at all to intrude into the cab. It is shown well here:
https://www.highlevelkits.co.uk/product-page/gwr-dean-goods
Having built High Level locomotives before, I’d also say that the quality of them is beyond superlative. Really easy to build and a joy to make with it.
best,
Paul