Since I am looking for a date correct block would it be to far off to use since it's a January 1971 Mounds Rd casting. Once painted all that would be visible is the casting date not the final assembly date. I would like to build a date correct 340 with lighter forged pistons and connecting rods and since the heads are X heads I'm looking to build a set of "J" heads which would be correct for the 71' year build. I have a great running May 1st, 1970 engine and I am not looking forward to spending more money for changes that the majority of people will never even notice but I feel the car is worth the effort .