Should a Composite Primary Key be clustered in SQL Server?

Consider this example table (assuming SQL Server 2005):

create table product_bill_of_materials
(
    parent_product_id int not null,
    child_product_id int not null,
    quantity int not null
)

I'm considering a composite primary key containing the two product_id columns (I'll definitely want a unique constraint) as opposed to a separate unique ID column. Question is, from a performance point of view, should that primary key be clustered?

Should I also create an index on each ID column so that lookups for the foreign keys are faster? I believe this table is going to get hit much more on reads than writes.