Pan gasket for 360. What one works best?

HI ,I'm new to this site but I hope someone can help me with my problem. Three years, three rebuilds and still leaks. so frustrated. so lets start from the beginning. started restoring my 74 duster 6 cyl. first bought a 360 out of 75 truck and sent to machine shop, cleaned , checked, bored long story short, replaced everything. car done engine in and started right up everything good. first time driving got a little oil leak around rear of pan. as i got more miles on it and started giving it more gas the worse the oil leak. oil pressure 30-40 ideling up to 80 when i step on it. let me get to the point it could take me all day to tell you the things i have done since the first build. #2 had machine shop recheck out but the crank had a small grove at the seal area but he said he didn't think that would cause a leak. got all together and still the oil leak. won't leak if i drive real easy. the more i get into it the wores it leaks. i can not tell exactly where the leak is, i have even tried dye in the oil. its always all around the back of the pan, there is nothing coming from the top of the engine. I changed the oil pan again and took out the high folume oil pump and put standard back in. still leaks. #3 pull engine again, put in new crank with premium seals, still leaks. please help me. is there a difference in the pans. i started out with a chrome oil pan and went to a dodge dealer and bought a factory pan still leaks. i put on a new PVC also have an exter breather cap. every time i think i have the problem solved. not so . any one else ever had this problem. "HELP"