so to the question: can i use the williams 1942 roms to replace the relevant capcom 1942 roms to convert my capcom 1942 board to williams 1942 ?
i replaced six files in the 1942.zip with six from the 1942w.zip file (different names in each set so had to rename them)
fired up mame, tested each of 1942 and 1942w and this worked, the only exception being an error reported by mame, presumeably because some or many of the CRC bytes no longer matched up to that known by mame for those i replaced in the 1942.zip set. so, i guess i'll have to suck it and see! any hints as to how to fix the crc info for mame so it doesnt complain ?
next step: burning 6 new roms for the capcom board, using the matching 6 williams 1942 roms.