I was able to get a Ford manual, which states 25-35 ft. pounds.  In
case anyone has this job before them, perhaps you may benefit from my
experience.  I started with a broken rear right exhaust manifold bolt
and warped manifold on my 1996 Class C Ford 460 w/130k miles.  I
sprayed the bolts with penetrating oil for a couple days, and I was
luckily able to remove all of them without breaking any.   I was also
fortunate that the broken bolt broke off at the bolt head and not the
cylinder head.  I was able to remove the broken stud with vise grips
after filing a couple flat spots on it to maximize the grip.  I bought
a "pass through" Gear Wrench ratchet set, to access the two front
bolts/studs, which worked great.  Had the manifold machined for $90.
I bought a replacement bolt from the Ford dealer for nearly $20.  I
initially tried to get all 8 replaced, but had problems getting them
ordered through my local dealer.  The 7 used ones went back in there
(saving me about $150), with plenty of high-temp anti-seize compound
and 26 ft. pounds of torque.  I decided to stay in the lower end of
the torque range, because of the friction reduction caused by the anti-
seize.  I had to go by feel on the front two using the pass-through
ratchet.  Total cost: about $175, including the ratchet set and jar of
anti-seize.  Total time: about 3 hours, not including shopping for the
ratchet set and driving to the machine shop.