KnitWit Pattern for Men's Alpaca Cardigan in Sizes 38-40-42 which is Medium to Large. This pattern is specifically designed to be used with Alpaca or Alpaca equivalent textile attributes. To get the right fit you need to use the pattern with fabrics which have the same weight and stretchability (or thereabouts) as Alpaca textiles from the 1970's.
Luckily, there are good alpaca/wool combinations available today which would suit this pattern as long as the weave is loose and it's not more than light to medium in weight. This should give you the two way stretch you need to make sure the pattern fits across the shoulders and in the sleeve as well as the length. It's a great pattern made from heavy weight paper. It's collectable too so it's best to take a copy to cut out your fabric and keep the original.
Note: You will need to make your own pattern for the welt pockets, the waitband, the cuffs and patches from measurements given. I have checked the pattern and these measurements include seam allowance even thought it does not say so. You will also need to be familiar with how to make welt pockets or just leave them out. They are a mock pocket. There is also no mention of how many buttons you need or what size buttons so it's up to you. You can choose large or small buttons and will need to calculate how far apart to make them. You can copy another cardigan for this or you can work it out yourself. Generally buttons are about 12cm apart but you can do whatever you want as long as the cardigan doesn't gap out too mucn inbetween buttons.
P.S.(You could use this for ladies as well because it's a loose style).
1. Button up front men's cardigan with back waistband, designed for alpaca fabric.