the simple way is to find some wheels you like
then get the granada hub flanges drilled to suit
then fit the granada hubs flanges to your hubs

it's a fairly straight forward swap and a good time to swap the bearings over, one big nut in the back at the front and one nut on the outside at the rear, just make sure they are tightened up to the correct torque

on the sierra the rears will comfortably take a 8 inch wide rim on an et45, the sierra rims were 17x8 running an et45 offset and wearing 215/45/17's and fitted perfectly