Like mentioned already, you need to get the cam , lifters , heads and rockers on that block and then measure. I like to take a stock push rod of the correct end style, be it ball/cup or ball/ball , cut it in half, lop off another 1/2 inch from one side and use smaller diameter "all thread" with nuts and fit the all thread inside each piece of the halved pushrod..using the nuts to adjust or separate them to the desired length that gives the correct amount of preload or lash.