When you chassis dyno, you want to run that in 4th or high gear.. If you ran it in 3rd yor #s will be lower from the final gear ratio of 1 to 1... With a 4x4 chassis and driveline expect a 28 - 30% loss with 5.13s. We have a dyno-jet at the shop where i work.
With a blown alky deal dont skimp on the ignition. Get a MSD Mag 20 at the min. On our 540 big chief stuff we went from a 20 to a 44 and picked up 125 hp at the wheel in my chassis. But thats all out high dollar stuff.