Restoman,
I cannot provide feedback regarding the EFI system, but I can comment regarding the cylinder heads.
You are correct that the stroker motor will wake up the throttle response of large port 4V heads in the lower rpm range. The 393 cubic inch motor will "fit" the size of the 4V intake ports much better as a street motor.
To take full advantage of the potential of your motor the 4V heads will require extensive porting and valve seat work by someone who "knows" the Cleveland heads; the exhaust system will need a good set of 1 7/8" tube headers and 2 1/2" tubing minimum between the collector and the mufflers. In lieu of spending money prepping a set of iron 4V heads, you might consider the alloy 4V heads manufactured by CHI.
The iron 2V heads with the 4V valves & porting will support 450 bhp, the best port jobs can support 500 bhp, but that's pretty much the limit of those heads. The intake port flow curve flattens out at 0.550" intake valve lift. The 2V heads work best with stock displacement motors, low rpm power bands, heavy vehicles, automatic transmissions and/or high rear end gearing ratios. They are good heads, but in your situation (installed in a Pantera motor of 393 cubic inches) they would not be advantageous, and in fact would very likely limit the potential of your motor and car.
With head porting, the right exhaust system, a good hydraulic roller cam & careful tuning, I would expect your 393 cubic inch motor to produce 480 to 500 ft/lbs of torque, and 500 to 550 bhp, depending upon the powerband.
Your friend on the DTBB, George
