kayarbro,
Yes, this can be done. We have done it in the shop for some customers, however, it is a lot more work than you might wish on yourself, involving a different master cylinder and linkage, MGB front suspension and brakes, MGA wheels if you have steel wheels, and a modified MGB rear axle and housing, modified to fit the TD. This is the only combination that will give you good disc brakes and the original look. In fact, once you put the TD hub caps on the MGA wheels nobody can tell at all, unless they know their T cars and lay down under the front end. If you have a taste for this, repost and when I finish the 12 page article I'm writing on it, I'll make sure you are notified.
Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon