PHR tested the SB engines & published the results in the Feb 69 issue. The reason for the testing was to see if the engines produced the adv hp. So engines were removed from factory stock cars & dyno tested.
Only one engine did....the 340. Not only did it produce the adv #, it made 20 hp more! 295 v 275 adv.
Here are the others: adv, measured hp
Olds 350 W-31 325, 280
Pont 350 HO 325, 255
Chev 350 300, 240
Ford 351 290, 210
The 351 is probably a Windsor, still finished last...
The writer commended how flexible the 340 was, could rev to 6500 without valve float & commented on how C had got the parts combination correct, including port size. A lesson for Ford in there...