hey guys i need help with some bolt sizes..

1. what size are the header bolts..( header to engine bolts)
2. what size are the lower header bolts ( header to exhaust bolts)
3. what size is the bolt on the driver side motor mount?

 

1. 3/8 (corrected) standard thread 1 1/4" long should work (I had factory w/z longer)
2. ??? 3/8" use brass nuts. If holes both sides, I would use largest bolt that will fit tight.
3. 5/8 standard thread - 1" long should work
this is from memory from 6 mths ago. please correct me if I am wrong.
sorry this would be for a 455, not sure about 350 my guess the same.

 

Head to exhaust flange bolts are 3/8 coarse not 7/16 unless BBO heads are different than SBO but I don't think that are.
On header pipes to collector all I have seen is 3/8 hole. I always use a bolt thats a little long and double nut it. Holds great but comes apart when needed much faster than a lock nut