EZ drain?

[76Tahiti]

Hi folks, I have a '76 Tahiti w/ a 455 in it that I'm doing some work on.
I'm going to install a EZ drain kit on it, so that I can throw away my pie pan I want to do it before I bolt up my exhaust logs in the next few weeks. I'm not sure what part I need to order though- anyone know off the top of their head?
Hardin Marine has 2 options, I think I need:
620-242179
E-Z Oil Drain Kit - Fits Drain Plug Holes With 1/2-20 Thread
http://www.hardin-marine.com/SearchR...oryID~180.aspx
...but, I'm not sure- rather than spending the money 2 times, I thought I'd ask around.
The boat hasn't seen much updating in the last 20 years, I'm hoping to get it up to snuff soon!
Thanks for the help!

[DelawareDave]

1/2-20 is the correct one. That's what mine is.

[El Prosecutor]

http://www.rexmar.com/page273.html

[76Tahiti]

Thanks guys!