best thing you could do is buy a donor car out of the j-yard if you can find one.
he is going to need a lot more parts than just mounts to make it work.
theres only a few things the 6 and 8 share.
and theres only a few things the 78 block and the 89 block share.
off the top of my head...he will need to change
obvious mounts and frame plates
oil pan is Mustang II specific , oil pump pick up tube,
the II uses a short water pump
the 75-78 timing cover is also needed because of the oil dipstick
transmission is MII specific. thats a big problem
the tunnel in these cars is very tight limiting what will fit without mods..
you will need MII manifolds or headers specific to the II.
i could go on and on but i dont know exactly what he has done or has collected for parts so far,
this is a job only for the well experienced, if he has everything he needs except for the mounts, then they can be found... do a search on the internet
for mustangII parts,
if you go into the parts section in this forum you will see a thread for
mustang II mounts, but no one here has tried em as far as i know
and you still need the mount frame plates which you wont find unless used.
nobody makes those.
if he is serious about this swap and has no parts for the II
the best bet is a donor v8 75-78 mustang II
other wise you could be collecting parts for quite a while..
this would have to be a project car and not a daily driver,
what does he have for a trans in the car and which rear end ?
is this a project car , and what happened to the v6?
does the car run and drive now??