hi
i wanted to do 390 swap about five years ago, did not happen because of life...
what i do remember is there is a bell housing to fit a t56 and a dry sump oil pan involved.
if you set the motor under the hood on the ground (on stock oil pan) and try to shut hood, you will
see why you need a dry sump.
as for power you need good heads, large carb(efi is better), good manifold, 10-to-1 compression, cam (if you use efi you can get a mean cam and have it run good).
i do not remember all my build specs, but i started on that motor in 00' and it was 3-or-4 years to find all of the parts at any kind of a deal. today it will be real expensive
to get close to the power this motor is capable of.
by the way my motor ended up rear wheel dynoing 487 hp and 512 ft lbs
good luck.