I'm planning on a 383 build. The Wiseco and Daimond Pistons are 3.903" and 3.905" bore. If I get my stock LS1 block honed by a machine shop, should I have them machine it to the exact piston diameter or a little larger? If so, how much larger?

 

before you take block there get the pistons you will be using and take them with you.
so he can measure the clearances, i know on the wisco there is a 4 thousands between the piston and cylinder wall, not sure on the diamonds

 

exactly what he said↑↑↑↑↑↑

They should also number each piston with a marker so you know which cylinder each pistons belongs to.

Also have the shop use a torque plate when honing the cylinders.