The AMG tuned version of the 4.3 M113 has 301 HP and 302 ft lb torque at the crank. Maybe it is just me, but that seems like an awful lot of work to still end up with less hp and torque than an SRT. If I were going to do a V8 conversion, I think I would want to be able to trounce an SRT when I was done. Or, are you planning on doing a turbo charged upgrade to it?

Good luck with the project.