[mjwood0]

Solution!!!
Well, I guess I'm going to answer my own question -- but am also going to make sure I post it so others may benefit.

The solution is ACL -- POSIX Access Control Lists

Now -- I must say, I don't really fully understand all the features here. But they are quite powerful and were pretty easy to make work in my situation.

So, to start with, download acl.

sudo apt-get install acl

At this point, you have to modify your fstab file for the mount you want to be able to use ACL. But first, unmount this folder.

sudo umount /dev/sda5

You will obviously have to replace "sda5" with the appropriate partition.

Then, edit the fstab file to add "acl" to the mount options. It should look like this:

/dev/sda5       /home/data      ext3    defaults,acl    0     0

At this point, you need to re-mount the drives. Easy way is:

sudo mount -a

Okay. So you're back in business. In my case the directory I want to be read, write, execute for everyone in the group "data" is /home/data.

To see the acl permissions on this file, do the following:

mjwood@mojave7:~$ getfacl /home/data
getfacl: Removing leading '/' from absolute path names
# file: home/data
# owner: root
# group: data
user::rwx
group::rwx
other::r--

This pretty much tells you the same thing as a "ls -al" command.

What I wanted to do, was set the default permissions on the directory to rwx for all users in the "data" group.

sudo setfacl -dm g:data:rwx /home/data

Repeating the getfacl command now gives me this:

getfacl /home/data
getfacl: Removing leading '/' from absolute path names
# file: home/data
# owner: root
# group: data
user::rwx
group::rwx
other::r--
default:user::rwx
default:group::rwx
default:group:data:rwx
default:mask::rwx
default:other::r--

From what I can tell, the options mean the following:
-d -- Set the default permissions
-m -- Modify the selected permission

the rest of the command is as follows:
"g" is that I want to set permissions based on a group
"data" is the group I want to set the permissions for
"rwx" are the permissions I want to set.

Just an important note in case anyone tries this -- to remove acl permissions, execute the following on the directory:

sudo setfacl -b /directory/to/remove/permissions/from

I tested this and everything under this directory inherits the default permissions. Works great for what I want!

Now I just have to see if this survives a reboot...

Hope this helps. If I get a chance, I'll try to write my first howto -- that is if anyone thinks it would be useful!