best plan - if you really want to go down the moustache route - might be to fit the bars to your existing stem, have a ride around, and see how it feels. you will probably be able to tell whether your setup needs adjusting by simply trying it out.
you should probably also check to make sure the brake cables are still the right length - depending on your old setup, the brake-to-lever distance might have changed and they'll be too long/short.
sorry if that's an obvious answer, or not what you were fishing for.
best plan - if you really want to go down the moustache route - might be to fit the bars to your existing stem, have a ride around, and see how it feels. you will probably be able to tell whether your setup needs adjusting by simply trying it out.
you should probably also check to make sure the brake cables are still the right length - depending on your old setup, the brake-to-lever distance might have changed and they'll be too long/short.
sorry if that's an obvious answer, or not what you were fishing for.