F.A.S.T. questions

[VintageMusclecar]

Asking purely hypothetical questions, of course...

Say someone were to contemplate building a `67 L78. The OEM heads are casting # 3904391, the carb is a #3910 and the intake is a #3885069. All rather expensive items in comparison to their more common 840, 4346 (et.al.) and 163 bretheren.

Would 840 heads, 4346 carbs (or any other similar design 780 GM carb) and a 163 intake be legal substitutes?

Next question: Did the F40 HD suspension option on `67's include a rear sway bar? If so, are aftermarket replacements legal? Do they have to be OEM diamater?

Last question (for now, anyhow);

F70/14's were an option on `67's. Do I understand correctly that a G70/14 is an acceptable upgrade, as long as the original 14X6 rim is maintained?

Thanks!

Eric