Beater: You would be surprised to know how much side play you can run with a GMC or any engine. The key is oil flow, and correct grinding of the crank when using a smaller diameter big end rod.(radius) It "appears" the Pontiac has quite a lot less diameter. If the GMC is done by a guy knowing what your plans are and he has the rod and bearing; the ginding can be done to use the narrower rod and maybe stroking it a bit too. This will also make for a shorter/lighter piston. The piston companies I have delt with will make them any way you wish, ie: pin height, pin diameter, ring width, clips/buttons, gas ported, etc. Good luck
