Postgresql apt repository naming scheme question

Hi,

Many packages in the Postgres apt repository (
https://wiki.postgresql.org/wiki/Apt) are named with a PG major version
postfix such as postgresql-client-9.5. Is there a reason why libpq-dev is
not?

Specifically, I'm interested installing Postgres 9.5 on Ubuntu 14.04, which
is made very easy thanks to the apt repo. But I don't see an easy way to
specify that I want libpq-dev (e.g, for rebuilding psycopg2) 9.5.something
instead of 9.6.something.

Is it safe/recommended to use the latest released libpq-dev package rather
than one which matches the major version of the serrver/client packages
being installed? Or should I be manually using the morgue as described in
https://www.postgresql.org/message-id/20160731194944.amiwidhsoqh4osac%40msg.df7cb.de
? I feel like I may be missing some key difference between -dev and non
-dev packages.

Thanks,

Jacob