Q: What's the best order of assembly of an M30 motor?

If you don't follow this order you will likely end up re-doing work.

1. Oil pump and chain.
2. Lower timing chain sprocket, guides, and timing chain.
3. Lower timing chain cover. Don't forget to install the brackets for the timing sensor and shackle.
4. Grub screw, AC compressor mount, PS/Alternator mount
5. Rear main seal.
6. Oil pan
7. Install harmonic balancer temporarily so you can see crank TDC. NOTE: in my pic above I am NOT at TDC. The crank dowel pointing up DOES NOT indicate TDC.
8. Set head to camshaft TDC before installing. TDC means the small dowel pin on camshaft is down and the two face bolts are aligned vertically.
9. Head.
10. Upper timing chain cover
11. The rest is straight forward

The Haynes Manual has this order:

1. Piston rings
2. Crankshaft and main bearings
3. Piston/connecting rod assemblies
4. Oil pump
5. Sump
6. Cylinder head assembly
7. Timing belt or chain and tensioner assemblies
8. Water pump
9. Timing belt or chain covers
10. Intake and exhaust manifolds
11. Valve cover
12. Engine rear plate
13. Flywheel/driveplate

Content originally from: M30 Engine Rebuild Tips & FAQ