Hy spanners, the Pontiac/GMC V8s were/are very reliable, the engineers at GMC had their pick of GM engines for the light/medium duty truck line, and they chose to use the Pontiac engine over all the others. Are they tunable, of coarse they are, they just require a little more research than the small block Chevy, to tell you what interchanges, and what works well, hope that helps.
