Also, remember if your old engine has failed the parts will all be contaminated with debris. The oil pump, sump, oil pickup, heads, oil feed lines, turbo and hoses etc will all need thorough cleaning and inspection. Valve clearances and seats will need to be checked, the head faces should be machined flat, new head studs or bolts shopuld be used. I always fit a new oil relief valve or new oil pump complete. The radiator should be serviced too.