340 ?

if it's a 1970 engine, the cylinder heads should be cast number 2531894. the J heads are more than likely dated mid 1971 to mid 1972. these are a good head also, and came on all the 360's those years. all 318-340's those years came with the same casting number rods, but the good 318-340 rods up until about 1971 have larger numbers about 5/16 inch high...those have the floating pin bushings. if they have the smaller cast numbers like 3/16 tall, they are the standard rods.