As far as I know, any Pontiac HEI distributor will drop right in, even
one out of the short-deck 265/301.  I picked up a random Pontiac HEI
distributor and dropped it into a '69 Pontiac 350 no problem (I seem
to recall a tech question a while back in one of the Pontiac mags
where someone had dropped a 301 distributor into an earlier engine).

Now, as I'm not *100% positive* that the 301 version will work, so
your safest bet is to find a 350/400/455 distributor.  However, I
expect that it will be easier to find a 265/301 in the junkyard
because those motors hung on a little longer, and a considerably less
valuable to Pontiac engine collectors.

A Chevy, Olds, etc. distributor won't work; don't bother.

You probably won't have any problems with a Catalina, but eyeball the
firewall clearance first--the HEI is considerably bulkier and greater
in diameter.  It fit in my '69 Firebird, but I had to clock it weird
to get just enough timing adjustment.