Does my junkyard 6.0 need machine-shop work before it goes in?

Not automatically. Test it first, and let the results decide:

• Compression or leakdown test: low or uneven numbers point to worn rings or valves.
• Oil consumption and blow-by: worn rings are common on high-mileage engines.
• Bottom-end noise and oil pressure: a knock or low pressure means bearings and crank work.

If it tests healthy, you can reasonably run it as-is with fresh gaskets and seals (plus a cam and springs if you're upgrading). If the cylinders are worn, Speedway's LQ4 guide notes you may need to overbore the block and fit oversize pistons — that's machine-shop work. See rebuild scope for a used 6.0.