Hi, I am not sure if your coach is similar to mine in terms of Ford fusing but there is also a 10 amp fuse in position 9 of the Power Distribution box in the engine bay that is labelled as starter relay coil; starter ground relay circuit. From your description I assume your reay flips were regarding relay #4? Ther are a couple of old Ford starter circuits on a web link if you scroll down it that might be similar to what you have .....the one that seems to go through the PCM (Power Control Module) may be the more modern schematic to use. There is not much else to check if the fuses and relays are good; you replaced the starter itself......so connections of key cabling and the chassis battery is about it. Hope this link works as I have had some issues with them in the past.
https://www.justanswer.com/ford/5ugu...-m-having.html