sounds like you have one rail type head and one non rail type

 

i found the mexican block by accident. i went to buy a weiand 174 blower off some guy for 1000 bucks when i got there he was asking me what i was working on... so he pulled out this 302 real clean all rebuilt, bored over 40 dont know if thats a good thing. but he sold it to me for 300. on another note what is the differnce between a rail type head and non rail type head.