Way back when Chris Higgs offered me a test build of the conversion chassis for the Farish pannier tank I always knew that it should have a new footplate. Alas I've had an almost complete chassis under an entirely unmodified body for around a decade. Moreover for my intended time period I also knew the body would require some changes beyond detailing to represent one of the predecessors of the 57xx class.
The photograph below shows how far I got in two days. Day one was spent machining off the cast running plate, followed by marking up and cutting out a new one. I used 0.4mm double sided copper clad with a view to providing the chassis insulation for the split frame in the underside of it. I also removed the top feed and various other details from the tanks. More than half of day two was spent making the splashers. First turning a couple if fat tubes with appropriate inside diameter and soldering a disc to create the front face. I got three splashers out of each of two discs. The coupling rod was used to mark off the splasher positions along the running plate. After soldering in place some awkward material removal remains under the splashers to create space for the wheels. What remained of the day allowed me to get a start on the buffer beams, valances and steps. All these are fretted and filed from n/s sheet. At the moment the rear is over long since I haven't finalised the exact engine and/or bunker size to determine the rear overhang.
Putting everything together I have some obvious dimensional differences. The can side is from a 28xx and dimensionally a little lacking in height. The tanks are I think still too high - as is the running plate, I think - but I can't get them much if any lower. Oddly the buffers appear to be the correct height against other rolling stock, which is weird. I've also cut the rear steps too short by around 1mm. The firebox still protrudes too much. There's quite a lot left to do but I need to ponder these dimensional issues before progressing further.
I deliberately haven't disclosed the class of engine. Maybe we should have answers in the comments. For those that don't remember or are new here (it has been 5 years) I'm aiming for early 1920s condition, which perhaps makes working this out a little harder.