Unfortunately, Abingdon did not begin adding the car color codes until the introduction of the TF. A bit of automotive archeology like you've done is necessary to build an educated guess as to the original colors for your car. The next problem you're going to run into is that the original paint was a "nitrocellulose lacquer", which is (or was - no longer made) very different from today's acrylic lacquer in color saturation and clarity. Remember, it was the cheapest stuff the Brits could get away with (several historical accounts state that US dealers would occasionally repaint new cars due to the poor condition/hue of the factory stuff), and unless you're going for a 100-point concourse museum quality restoration, or really enjoy repainting your MG every 2 years, you may wish to "improve" your car in this respect, and no one will knock you for it.
A Brit has put together a web site for all things "TD". Here's the link for his colors section - very extensive, well researched
http://www.mgcars.org.uk/mgtd/mgtd_finishes.htm
Another excellent source and authoritative reference for TD colors is the latest edition of the New England MG "T" Register's "The "T" Series MG Handbook". Page 47-48 and a new appendix "Paint For The "T" Series MG" by Hal Kramer are a wealth of information on factory colors.
There's lots of really red TDs, green TDs, black TDs, yellow and white. Some are now painting the car in two-tone, with the fenders darker than the body, with wonderful visual effect. The MG SA, VA saloon crowd has been doing that for years, and the cars are gorgeous. I painted mine with a Chrysler dark red clear coat, which matched the original "Autumn Red" pretty well. Of course, the clear coat is totally "wrong" but the color and depth really highlights the curves of the sheetmetal. The car is a real crowd pleaser, with "Best of Show" awards, but I'll never claim it's concourse original. No one cares.
Bottom line - it's YOUR car. Paint it any color YOU like. It'll look great!