Aluminum heads with cast iron manifolds, header gasket or oem style exhaust gasket?
Or C), no difference and I've already thought too much about it.

I would probably use what I had on hand, if I had to buy some I would buy a decent set of header gaskets due to the expansion rate differences between cast iron and aluminum.
You will need to retighten them several times until the fasteners take a permanent set

To be honest, its the expansion rate part that was making me rethink the oem vs the typical header gasket. Thanks.

I should have put in to retighten until the gaskets quit compressing and the fasteners take a permanent set

Cab Burge: if the fasteners have undergone a permanent set, then it's time to buy new ones.

http://catalog.remflex.com/MOPAR_Header_Exhaust_Manifold_Gasket_p/6003.htm

these are what you want these are the best and are reusable and will not leak .

Not in my opinion, once they hold the torque and don't need further tightening after several more heat cycles why would YOU replace them

Only ones I would use.

Not a problem since I installed remflex....

I prefer no gasket with thick flange headers and AL heads. Just a thin coat of RTV.

I would run the same with manifolds... after making sure they are flat.

you can't be serious .

A freshly machined aluminum exhaust flange mated to a cast iron manifold. I would expect any gasket to seal that up 100%.

High temp copper rtv is great for sealing stubborn header and collector gaskets. No reason why it wouldn't work on cast iron manifolds too. It doesn't take much - just a thin skim.

It has worked great.

Also recommended by some header manufacturers. The factory generally did not use gaskets at all with manifolds. That way there is nothing to blow out.

The point of tightening a bolt is to put it in tension, which means stretching, without having a permanent set. If that has happened you have overtorqued it, and you cannot apply the correct torque to it anymore,and the bolt will eventually fail due to loosening or breaking. Ask any decent engine builder!

The point is...
an exhaust bolt or nut will need to be re-tightened until it no longer gets loose.
I don't use aluminum heads so I can't say what is used for a gasket.
I use no gasket on exhaust manifolds.

Works great. Its all Ive been using for years now, even on collector flanges.

Me too, I've used a thin coat of high temp RTV and or gaskets with a spray coat of Permatex "High Tack" 99MA the thin red spray in the purple can more for its' holding ability than for the gasket sealing (tho it does seal up) & had no issues either way. most header gaskets ain't cut to an exact match to the port so I trim it if too big or cut my own if too small

Same here. For fasteners, I installed these:

http://www.stage8.com/

You are correct that a bolt has to be under tension to hold. However it can lose tension by other means than exceeding the elastic limit. One of those is having an intermediary material that compresses or flows over time.