You can assume that. But some that are close you have to just I stall them and see. The .381 is a good starting point, but these are castings. Each casting may have a few thousandths ( or more?) of variation on the non machined surfaces. Its cheaper to cast the part and machine down your tolerances then to have those tolerances built into the initial cast.
2001 ZX3 2.0L Zetec-
Hatch Nation #42
Going through Rebuild See "The TICK Build Thread" for details (http://www.focusfanatics.com/forum/showthread.php?t=289168&referrerid=62897)