If you know the right sizes it should be for 1/32 then simply adjust scaling in Lychee to suit.
917/20 spec -> 1971 Porsche 917/20 Specifications - Ultimatecarpage.com
So 1/32 width should be 69.1mm max overall width.
917/20 spec -> 1971 Porsche 917/20 Specifications - Ultimatecarpage.com
So 1/32 width should be 69.1mm max overall width.