I been turning wrenches for better than 20 yrs, & I have never seen a 305 run 30* cooler than a 350. I am sure they run a little cooler as there is more metal around the cylinders, but in the 39 Tudor case, if the engine ran fine in another vehicle the problem is radiator sizing. Yes, you need more radiator surface area for more cubes. Just because the radiator is thicker(more rows) doesn't mean it will cool as well as a larger surface area radiator. Brian
