I absolutely destroyed the original 7 1/4 in my 1970 Dart Custom in 1976, with a stock 318 2bbl. Broke the spiders and pieces went everywhere!!! Swapped in an 8 3/4 that is still in the car and doing fine, thank you very much. The car has had a 340 in it since 1978 and the 8 3/4 has over 150,000 miles on it...
I also destroyed my 7 1/4 behind a 340 with a T5 five speed. Revved it, dumped it and every gear came off the ring. Has 8 3/4 now and T56 magnum. No more issues.