[jaycoburn]

Steve, the #12 heads are not assembled right now. But as Cliff points out, it sounds like the swap from the #143's to the #12's really won't be worth the time/cost if I was seeking any real significant return on gained performance (based on my cam & probably the tranny).
Thank you for your interest in this thread.

[Dragncar]

For 1600$ SD can do a 270+ cfm race CNC job. I sent them a set of 48s and they came back looking as good as you can get a iron head. New race valves, full bronze guides, filled crossover, cc,ed, every surface milled to a mirror finish, Ti retainers, roller springs, hardened seats ect. Flowed 272.
Now if you do THAT to your 12s they thing will make a lot more power.
I had to sell them but will send SD another set of 48s to do the same thing to. Its a good deal really.
I would take a set like them in some 400 builds vs stock E heads any day.

[steve25]

Then again for 500 bucks you can yank that 068 Cam out of there & get a better one, get the Heads set up for more valve lift with a spring change and have a good Chunk of added power.

The question really comes down to how much of a HP increase are you looking for?
Big valve D port heads reworked to flow in the 270s and the port area that comes along with it and the level of Cam needed to make usage of that flow will kick up the motors power curve by near 2k rpm, is this what your looking for ?

If so then your cast Pistons will need to go!

A 400 built this way will need to shift at between 6200 and 6400 rpm and your short block is not built to do that!
You can make near 400 HP out of those 12s with the right Cam , is that a ok HP gain for you?

[jaycoburn]

Steve, I often forget the weight of these cars & the AT tend to conspire against what is perceived as real performance. I say this from the perspective of someone who also has a '66 mustang coupe with a stockish 302 (it does'nt take much to move that car). The '66 Lemans weighs almost double. I went into this build thinking for all intents & purposes it would ultimately be a cruiser. I think if I had done anything different I should have held out for a pair of the big valve heads. That said I am really not disapointed with the car. It's still brings joy to drive it (I barely have 600 miles on it right now). I guess I am having a case of "what if's" therefore the original post.
I would like to do a dyno & recurve the dizzy & see what that does. I am told by the machine shop that with this build (& the #143 heads) I am at about 9.5 cr & should be in the 300 hp range output. If that bears out then (in a perfect world) another 50 HP might be more my taste in this vehicle.