looking to find specs on 340-X heads.

340srule, I agree..the 340's do rule. But I must respectfully disagree on the '70 model 340 heads. They were the 'J' 915 castings and yes they came with 2.020 valves. I have had several sets of them myself. The 894 'X' castings were used on the '68 and '69 340's only. Might have been a few very early '70 models with them but the official casting for 1970 tru 1973 was the 'J' 915 castings. No question about this at all. Do you remember the six-pac heads with the pushrod hole machined for offset rockers ? Well those were 'J' 915 castings and the year was 1970. Also the first year for the 360 was 1971. They had 'J' 915 castings. And the year was 1971. The 915 castings had 2.020 intake valves in 1970 and 1971. 1972 and 1973 340's and all 360's 1971 -1973 with 'J' heads had 1.880 intake valves. As did all 360's. But..as was stated above, all the LA heads were almost identical in performance and flow, with same valve sizes of course. One years castings weren't really any better than another. Actually there's probably more difference in two different flow benches than in the different castings themselves. And they all respond the same way to the same port mods. So unless you have to have a 'correct' years casting..use what you have they are all good. Terry.