904 Trans safety question

Here's a question I've been tossing around in my mind for a few weeks now. I'm building a 66 Dart with a 408 mated to a 904. I plan on doing some racing 3-4 times a year. Should I buy a trans shield to be safe or is it only the 727 trans that explode. I've searched for info on this but only find stories of 727. I don't like taking chances but if it's not needed I don't want to spend the money. Shields are $300. Also if I do need it how well do the shields fit the early A body cars. Anyone running one that has pics they can post.
Thanks Rod