There are literally many dozens and dozens of parameters that engineers consider when designing an engine. And simply comparing only one or two of them between engines that might have one of them in common with the other is a common mistake that happens when someone is set on starting a build such as this. The parameters alone that the cylinder head brings into the equation are a big part of why one engine can have a long rod such as the Jag, and the GMC be better suited with a shorter one, even though they may have the same stroke or other similarities. The Jag also has a complex computer system that compensates for things such as timing and fuel curve that the GMC does not have that may make it "appear" to have a lot of low end when its really the computer system tricking you and manipulating things to make it seem that it does. Good luck with your project.
