There were 2 variants of the M60: The B30 (3.0L) and the B40 (4.0L). Based on the power output differences of the two engines, it is wise to swap the B40 variant. Unless you have emissions or displacement restrictions in your township, don’t swap the B30. There are instances of people swapping in B30’s due to regulations in their country.

If all that is available is the B30 and there is a desire to swap parts to make a B40, it’s not worth the hassle. All major engine components need to be changed including the heads, block, and crankshaft. The M60 block has the ability to be honed and fitted with iron liners by many providers if necessary.

Please see Table 1 for more information of applicability.

Table 1 M60 Generations (Wikipedia)