I have a 68 El Camino with a SBC. Block casting number is 3970010 which, I've read, can be a 307, 327 or a 350. The number stamped on the front pad under the alternator is MB04800. The MB is listed as either a 1967 327 or a 1968 307. In trying to decipher this ID code I thought that the M indicated Mexico. The 0480 to be the dates of April, 1980. Not sure about the extra "0". This is the information I found while trying to solve a fuel problem. I have replaced everything from, and including, the fuel tank all the way to, and including, the carburetor. Not sure if I have the correct fuel pump. Any help will be greatly appreciated.