Your easiest way to use a 727 converter would be to find a 2 wire 518 . 2 wires are non lockup , look for trucks or vans '89-'91 with a 2 wire connector . The 518s that require a lockup converter have a 3 wire connector . Any 2 wire 518 will use a 727 converter . Your question was can a lockup 518 be converted to a non lockup . I think the answer is yes but would be more involved , it would be easier to look for a 2 wire transmission . I have a 2 wire 518 in a '38 Plymouth with a 408 engine . I am running a PTC 727 converter .
'65 Belvedere II - 446-Indy,727 transbrake,Dana 4.56
'38 Plymouth 4Dr - 408SixPack, A518, Dana60 4:10
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