Rear leaf replacement suggestion

I am dropping in a 1500HP(well maybe 400HP)340 in my 69 Dart.
I have a fresh 8-3/4 with 3.91 sure grip and the shock mounting hardware.
But i don't think the old 38 year old rear leafs built for a low hp engine/drivetrain will be able to handle the extra torque.
So....what rear leafs should I buy as a replacement/upgrade?
Thank,
Doug
Author: admin