My new severe duty #2799 Hayden fan clutch is so much thicker than my old one it misses my radiator by only 1/4". These big blocks are about 3" wider, 3" longer, and 3" taller than the small blocks so they just BARELY fit in the C3 engine compartments. When I set it onto safety stands and run it the fan blades go "ding ding ding ding ding ding ding" as they hit the top fan shroud bracket bolts. Last year I slotted two 5/16" carriage bolts and used them instead of the 5/16" OEM hex bolts.