Hi, new member from Arkansas. Am hoping someone can help me out. I have a 75 ford bronco I bought about 15 years ago, just did a frame off restore on it, now I've working on the motor. The guy I bought the truck from had swapped out the engine, he said he was from a mustang, but I dont know. I always thought it was a 302 engine. Always bought parts for a 302 and everything's always worked. I decided to freshen the engine up so I bought a complete rebuild kit. On the side of the block is a plate riveted on and it states (bore .030 main .010 rod.010), so when I ordered my rebuild kit I ordered a 302 kit with the above numbers. I install the new cam bearings and new cam, install the new main bearings and all is good until I get the the pistons. The new pistons are way to big. I ordered assuming it was a 302 bored .030 over. So I measure the bore and it's between 3 5/8 and 3 11/16. I only used a tape measure to get the approx size. But it's nowhere close to a 4.0 bore. What have I got? There is no cast number above the starter. I did find a number on the opposite side of the block that reads E0?E, can't really make out what the third digit is but it doesn't look like a standard 302 cast number like on my 73 bronco. Could someone help. Thanks