A while ago I gave an old chuck a new life as a 3c collet chuck, as I had a set of 3c collets for the George Thomas VHD I thought they might be a useful for the Myford, but of course they don’t fit the Myford spindle so I came up with this :-

Basically I removed the chuck jaw slots and attached a threaded adaptor to the scroll which draws in the collets as you turn the chuck key. On final assembly I bored the nose piece Number 3 morse to suit a Boxford adaptor I obtained from ebay.
Andy.