Convert the BSP to a Map file.
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www.thewall.de for the BSP2Map Converter.
Convert the map, check the Map for Broken or damaged Blocks, resave the Map, open it with the MED...
This could be done within less 5 minutes...
But the Texture WAD files are not same, like the 3DGS WAD files. So youll must create your own Textures and re-Texture the whole Map !
hope this helps a lot
cYa Sebastian