index organized tables use case

Hello,
I'm thinking about migrating from another DBMS to postgresql. I have an
almost working proof of concept, but still have some doubts about the
following use case.

I have a table like the following

CREATE TABLE test
(
  code character varying(32) NOT NULL,
  tag integer NOT NULL,
  value double precision,
  CONSTRAINT test_pkey PRIMARY KEY (code, tag)
);

It represents a sequence (with holes) of values associated with a code.
The application code usually performs selection queries like

select tag, value from test where code='XXX';

also, deletions are like

delete from test where code='XXX';

and insertions follow the same pattern (all the data for a code is
inserted using a loop in a single transaction). That's more or less all.

so this type of workload is greatly enhanced by an index-organized table
(oracle) or a clustered index (SQL Server/Sybase).

From what I understood this kind of table is presently not supported by
postgresql (is it?) so, what do you advice?

I would think about something like

CREATE TABLE testnew
(
  code character varying(32) NOT NULL,
  first_tag integer, /* the tag value associated with the first value */
  "values" double precision[], /* the datum, or NaN if not valid */
  valid_values bit(1)[], /* true if a datum is present */
  CONSTRAINT testnew_pkey PRIMARY KEY (code)
);

but this would require an application refactoring. Any idea?

TIA,
e.