I can offer some experience with the head issue, ..
First, .. if it's a limited street, .. just go ahead and put some
compression in it, .. 15:1, .. you're giving up too much to use
a fuel that doesn't belong in a $20K engine.
a GOOD 24* conventional style head will make well over 1000 hp
on an engine this size with a race style build, ..
but a good spread port will be better.
We build an Edelbrock 24* with a 2.4" intake valve that does this, ..
http://www.racingjunk.com/post/92317...ictor-CnC.html
but a Good Brodix 1803 with a CnC port will make around 70 more, ..
and if you go to a well ported Dart 11* and 15.1 comp you'll be able
to make 1250 - 1300, ..
As far as chamber and valve angles, like the Dart 18*.
the primary performance gain is in the chamber and flame travel, ..
smaller dome etc. In a 11:1 engine I don't think you'll see much
difference between Dart's 24* and 18* heads because you're not taking
advantage of the better head.
Now with conventional 24* VS a spread / raised port style head
like a 14* Dart big chief you will see a difference because of
the more efficient port design and port velocity profiles, ..
Curtis