Ingrediants for Guinness Extra Stout Recipe

I’m making the Tess and Mark Szamatulski recipe. For the steeping grains it calls for British crystal malt and acid malt. What ones do you recommend? Do you think Mountmellick light malt is essential versus NB’s malt?

Thank you!

Didn’t BYO have a good recipe for this beer I’m not a big fan of their recipes.