Need help 'converting' 1964 Vogue Knitting pattern (size 42?) to 2011 Size 12

Have a friend who is wanting to knit a sweater dress from the Spring/Summer 1964 issue of Vogue Knitting (pattern #41 if you have access) ... my friend is a size 10-12, which by 1964 sizing would put her at a size 42 ... and the max size of the pattern is Size 16. Any advice, suggestions, direction? I did contact Vogue and they declined to 'customize' ... I'm only looking for advice.