To heck with the engine block angle, just eyeball it for level and to where it looks nice. This angle is not important but if you could borrow an intake and just set it on the block, even without heads, then a level on the carb flange would put you dead on. What is important is that your pinion angle is down 3 degrees (2-4 degrees) from your crank centerline. This is supposed to rotate the needle bearings in the U-joint cups to extend life and push the slip joint deeper onto the trans output splines under acceleration. Your concern for correct angle needs to be when you install the rear end housing. If engines had to be at a precise angle to run then no cars with carburetors would be able to be driven in San Francisco.
