Best TCP port number range for internal applications

Question

I work in a place where each of our internal applications runs on an individual Tomcat instance and uses a specific TCP port. What would be the best IANA port range to use for these apps in order to avoid port number collisions with any other process on the server?

Based on http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml, these are the options as I currently see them:

1. System Ports (0-1023): I don't want to use any of these ports because the server may be running services on standard ports in this range
2. User Ports (1024-49151): Given that the applications are internal I don't intend to request IANA to reserve a number for any of our applications. However, I'd like to reduce the likelihood of the same port being used by another process, e.g., Oracle Net Listener on 1521.
3. Dynamic and/or Private Ports (49152-65535): This range is ideal for custom port numbers. My only concern is if this were to happen:

a. I configure one of my applications to use port X
b. The application is down for a few minutes or hours (depending on the nature of the app), leaving the port unused for a little while,
c. The operating system allocates port number X to another process, for instance, when that process acts as a client requiring a TCP connection to another server. This succeeds given that it falls within the dynamic range and X is currently unused as far as the operating system is concerned, and
d. The app fails to start because port X is already in use

Answer 1

I decided to download the assigned port numbers from IANA, filter out the used ports, and sort each "Unassigned" range in order of most ports available, descending. This did not work, since the csv file has ranges marked as "Unassigned" that overlap other port number reservations. I manually expanded the ranges of assigned port numbers, leaving me with a list of all assigned port numbers. I then sorted that list and generated my own list of unassigned ranges.

Since this stackoverflow.com page ranked very high in my search about the topic, I figured I'd post the largest ranges here for anyone else who is interested. These are for both TCP and UDP where the number of ports in the range is at least 500.

Total   Start   End
829     29170   29998
815     38866   39680
710     41798   42507
681     43442   44122
661     46337   46997
643     35358   36000
609     36866   37474
596     38204   38799
592     33657   34248
571     30261   30831
563     41231   41793
542     21011   21552
528     28590   29117
521     14415   14935
510     26490   26999

Source (via the CSV download button):

http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml