1) do you have to buy the adapter? Depends on what you consider a job properly done. Some will tell you to break the collapsible joint pins and alter the length of the column to make it fit. One wonders why the factory did not do that.

2)do you need the fast ratio idler, no. In one of the DC chassis books there is a quote that says they looked at using a longer idler to match the pitman arm and the "benefit" was slight and deemed not necessary.

You could of just kept your stock 24:1 ratio box and used a steering quickener.

and got 12:1 without idler, pitman arm changes or interference with headers or oil pan.