hard engine-braking in second gear- will this wreck a 904/727?

I've been spending every free minute of my life in the garage lately and I'm hoping to be ready for some autocross before the end of the season. Someday I will have the resources to swap in a proper manual box but that's going to take me years to save up.

So I still have some unanswered questions about running this car, not the least of which is what's going to happen to the transmission under typical autocross flogging. I am running an A904 with some upgraded internals and a deep pan but no manual-shift valve body and IIRC, a stock sprag assembly. Probably also worth noting is that the transmission is spinning a 4.10 axle.

Often in autocoss, the transmission (auto or manual) would be left in second gear which means that you alternate between heavy throttle and closed throttle often. This can often be a means to get the car to rotate through some engine braking forces on the rear wheels. Also with a V8/rwd car, there's a very good chance for lots of tire spinning at various points on a given autocross course.

Will these conditions spell certain doom for a Torqueflight? Is this asking for sprag-destruction?

Currently, I'm sliding around on no-season BFG T/As but at some point I will have the cash for some modern/sticky rubber. Safe to say that the risk of damage will only go up?

Thanks for any insight/experience!
Mike