i used to work on a lot of the olds diesels,they had all kinds of problems but mostly head gaskets from broken head bolts,the gm ones were really hard and were torqued to 130#,ive seen several with the heads popped off,i got to using grade 8 bolts from Caterpillar with a hardened washer under the head,torqued to 125# in 4 steps,never had a problem, with them,once in a while one would stretch when installing but it didn't break just got skinny between the threads and the head