Speaking from experience, I broke multiple 8 3/4 rearends with a mild 440 and a 4 speed in my old '68 Charger R/T. Axles, yoke, a pinion in half, etc. If you launch it hard at all, you're going to break parts. Sell what you have and use part of the proceeds to finance a Dana or 9".

The only other option is to never put drag radials or slicks on it, and slip the clutch on launches.