Try these sites.

NV4500 Transmissions - Adapters - NV4500 Conversion Kits | NV4500.COM

Crate Engines, Stroker Engines & other Custom High Performance Engines - BluePrint Engines.com

They have some nice 383 strokers designed for low end torque that would be ideal for what your wanting to do. Then you could find a NV4500 out of a Dodge or Chevy and have a bullet proof set-up that had great road manners and stump pulling torque between idle-5500 RPM. Could still run power streering and brakes too.