Is it a 383 or a 361?

If you look at the pad that is just below the distributor it will tell you what the engine is . There will be letters and numbers stamped on the block . The letters indicate the year , numbers indicate the day . Also the cubic inch is stamped there also . Example ; a 36 or a 361 would indicate a 361 , sometimes 61 is visible . The same for 383 , a 383, 38 , or 83 . Also look for a letter P for passanger , M or I stands for marine or industrial . Not sure about trucks, though . Hope this helps . The block casting number is on the side of the block but is usually hidden by the exhaust manifold . Hope this helps .