It really needs to be back braced for sure. I did it on my street car before I put the rear in. Bending at the perches is a common issue when you hit them hard.
FWIW a buddy of mine has an 8 3/4 in his Dart, 620 HP and hits it at 3400 off of the trans brake. His holds up just fine. It is shortened some with the brace and after market axles.