the 1969 to 1975 heads are fine to rework.
Here is one from Youtube
http://i1215.photobucket.com/albums/cc5 ... I6head.png
You keep the exhast, and just focus on the intake profiles, and make it easy, not hard.
It lookes like you've killed it with a grinder when its first done, like Mr Comet's and FALCONAROUND, but after a trim up, it allows the best intake around
http://i1290.photobucket.com/albums/b52 ... 5-orig.jpg
You can make more power with a nice cut off log and a close to high ported head than anything else. I've got a 6-bbl kit I'm working on, with three 350 cfm carbs grouped together. So it doens't have to be exotic.
As for why we;ve not done any sixes...
Nothing to do since 1962...it was the AC Cobra era, and the Shelby modified AC killed the 170 HP Raymond Mays Zephyr six with its stock 164 and 195 snd 271 hp 260's and 289's. Then after the FE 427, the GT40 289 and Boss 302 sort of cemented the feet of any I6 illusions of granduer.
brothers, we forgot our names, we forgot it on the wall paying tick tac toe....
More to the point, as soon as people in the USA started having so much fun with Windsor 289's, Boss 302 and 351's and especially, those fearsome FE and Limas, no-one did any of that kewl stuff to there Ford sixes again except for Ak Millar and Bruce Sizemore and the Mad Frenchman...it was a dead poets society. 4 and 2-bbl standard cost control small and big blocks were the new fun.
The Aussies did all that hackmiester indendent runner Duggan/Irving/ Dave Dyno Benett stuff right as the huge inflation of post 1973 living just drove the high powered street sedans movement to the speedway, and the cash strapped Argentinians just shoved low drag body kits on there 60's and 70's Valiants, Falcons, Commodores and Torinos, and used 2-bbl carbs and 3 to 4 liter sixes as 350 to 400 hp power houses. The Duggan head would make 370 hp on 202.
http://i1215.photobucket.com/albums/cc5 ... 2099-1.jpg
The missing link was when the guys in the US in about 1997 after the last shutdown, started hacking up log heads and slapping 250's into Foxes and 300's in to Falcons. Its taken about 60 years for people to get back towards the health of the Hudson Hornet era, were sixes and not eights, were the weapon of choice. But the Hot One ended that, and a time of great production 200 to 430 hp small and big blocks romped in the sun. Hey, I love the V8's but if little iron I6's in fat 2600 to 3800 pound Fords can run flat 10's without a hair dryer, I haven't seen them. The movement has died, but this effort might spike it up again.