Doing an informal survey. For bolt replacement for the exhaust manifold, what do you prefer to put back. It's an M8x1.25 thread pitch and about 56mm in length. Do you put Hex bolts back in there or do you put threaded M8 x 1.25 studs with the flange nut. Which would you do and why.....

 

Use stainless steel 12.9 , allen head bolts, if possable. Make sure your maniflod is flat across all four ports, that is a MUST. if your manifold isnt flat with a strait edge, dont bother to do anything, bolts will come loose or break, anyway.
Put high temp neverseize ( copper coat)
on ea bolt, and hand torque to specs. All will be good.
my 2 cents ( after many, many, manifold replacements)

 

Allen versus Hex cap bolts? Isn't that a bit scary? I would think that hex cap would be better.

 

Studs are generally used across the industry in exhaust manifold applications. They are theoretically better from a stress/strain perspective. Also they make installation much easier.

Ford offers the post TSB studs and nuts, which are stainless steel. I used nickel based anti seize.
W703902-S403
W701706-S2

ARP would be another good option.

 

It looks like the part numbers you referenced have a torx head? Is that using an "E" socket? These are stainless steel studs?

 

I have used SS bolts also, but on some manifolds, there is a shortage of room for the socket to fit on good. If there is room on your manifold, use bolts.
I used grade 8, thicker washers, ss allen head bolts on my 03 7.3. Torqued them, all is good. I dont use an impact to install them either.
i use the high temp ultra copper, because it takes the heat better,
APR stuff is good, but more expensive.
if the stuff from ford was good, you wouldnt be replacing them.
just my 2 cents