I noticed when I pulled my engine out that it only has 2 freeze plugs per side, well i only see one per side, but it looks like there is another behind each motor mount bracket. I remeber something about the clocks with 2 freeze plugs being more rare. How rare are we talking about? I will pull the heads off and see if it has been bored over. Lets say its a 2 bolt, 2 freeze plug .030 over block; how much would it be worth?

EDIT: Just went outside and got the casting #. Its 3951509 which is listed as either a 70-71 4 bolt block or a 74-80 2 bolt block. Beats me why they would have the same # for 2 different blocks. But there is another number on the back which I am pretty sure is the date code. Its H21 8. There is a space between the H21 and the 8 like a date code. I am not sure if this means august 21, 1978 or august 21, 1980. Anyone know which it is? Either way it should be 2 bolt, but I wont be sure until i get the pan off tomorrow.

 

if it's already been taken oversize once before it'd hurt the value a lot, and the number of freeze plugs doesn't mean much, other than it being a 400 or other SBC

 

I think the early 400s had 3 freeze plugs per side, but for the last years they made them the had only 2.