Yes 4" Bore, Brian checked it all out and it is good. I switched to 360 pistons to go with the 3.58 crank I thought I had when I found out it could be bored to 4.0..........Butttttt then the crank was found out to be a 4.0 so switched the pistons out to forged KB units and now it is a 402
Justin, this is one of the blocks I got from you!!