Bill Eaton
There is a lengthy thread on RMWeb headed “OO Gauge GWR Mogul and Prairie” which includes a number of posts by Frank Davies, who has built a new chassis for the Mogul which begs the question whether a conversion is even possible. This link might take you there:
https://www.rmweb.co.uk/community/index.php?/topic/129125-oo-gauge-gwr-mogul-and-prairie/