1969 small block cast waterpump bolt lenghts

Just finishing off the rebuild on a 1969 340 with cast waterpump-what are the correct bolt lenghts ---They seem to be sets available for 70 and up but they would be longer because of the aluminum waterpump

I dont have a pump in front of me but what I would do is stick some bolts into it on your bench with some lock washers & you want (iirc) 1&1/4 times or a slight bit more than the bolt shank dia, that length of threads to engage into the block. add in the timing cover thickness & its (2) gaskets

I always run a bolt in all the holes till it lightly bottoms out in the block then measure for the proper length. This ensures your bolts aren't too short or long. You DONT want a bolt to bottom out in the block on the actual install!

Yup, a bolt too long WILL break the cylinder wall, it's been done.