i just purchased a 350 enigne that has seen better days and my son and i plan on rebuilding it. it needs alot of attention, right now the only numbers i can find is HECHO EN MEXICO and the numbers 3970010 under it. do I need to pull the oil pan to find out if it is a 2bolt or 4? Still have alot of years to clean off and missing alot of parts. looking forward to spending some quality time with my son during this rebirth.