This is a question for those who really know thier 335 series. I'm going to be rebuilding the engine that was in my '79 when I bought it. My question is when I pulled this engine I think the valve cover sticker (sticker now gone)said it was a 400. i've ran the vin on the truck it says it came originally with the 351. My hi-per ford book says the only way to tell the difference between the two is to measure the stroke. My question is when I pulled the pistons they are stamped with a 400. Does that stand for 4.00" bore(both have same bore), or stand for 400 cu. I'm thinking I want to build a 400 but, mainly want to know of some way of knowing for sure what I'm starting with. By the way when I pulled this motor it had the 11" clutch(351M) but, I know they are interchangable with the 12". (As far as crank patterns) Any help would be great.