I have had cars in the shop for months on big builds. Custom pistons best case are two weeks and can be as long as 8 weeks. You can't order them until you tear down the engine. With larger builds scope creep sets in. As long as we have gone this far let's do this.
The build you describe is something that seems reasonably predictable. When you see the shop owner or manager ask for a completion date. That is very reasonable and serves the interest of the customer and shop.
So how long do you think this build will take?
Day 1

Day 4

Day 12

The motor was a basket case.
So how long will it take to finish???