Here is a list of reported flow numbers, but it's hard to really make a comparison as I can't tell if the big block and small block numbers were flowed with the same machine, procedure, and port radius or not?
http://users.erols.com/srweiss/tablehdc.htmIf your comparing stock to stock, then the numbers to look at would be around 0.400" to 0.500" because the stock cams only opened to mid .400 lifts
340 is 0.429"/0.444" lift, 268/276 duration - J head at 0.400" looks to be about 190 cfm, 0.500" maybe 200 cfm?
440 is 0.450"/0.455" lift 268/284 duration - small valve 516 looks to be about 10 cfm better? maybe 200/210 cfm?
The 906/452 looks to be about 25+ cfm better, around 215/225 cfm?