Alright, my brother-in-law has a 1991 Notch 5.0. He bought it knowing that the coolant was mixing with the oil, so he wanted help pulling the motor. Which we did, and threw it on the engine stand. Thinking it was a BHG, we tore the heads off, and found no BHG. So since the motor was out of the car, we proceeded to rebuild it. I only could help a little at this point, so he finished it himself. He took shortcuts, such as not replacing main seals, and other lower end seals. Also the waterpump gasket in the felpro gasket set was different, so instead of going to town to get the right one, he just "made it work" with modification and RTV. I have given up on giving him advice, so I just let him do it. Well once we got the motor back in, it fired up instantly. But after a little driving, we noticed coolant in oil again. He is automatically assuming that it is a cracked block. I dont believe it. Keep in mind that he didnt have ANYTHING checked while it was off. The heads: no. The intake was not machined or checked, which my uncle (built Late Model engines) said to do. Nothing was checked, just taken apart and thrown back together. So there the poor mustang sits...it runs great still, but has coolant in oil. Also, not sure if it has anything to do with the problem, but it starts like a carbed engine. You need to give it throttle to get it to fire up (e303 cams?) . So what could cause this? Or could it actually be a cracked block?