The aftermarket perfprmance parts for a 390 are very limited (as 69mach1 said) and can also be more costly, because they are not as popular. How about a 351W stroked to 392. Plenty of aftermarket parts for that stroker. Its unfortunate that you are in NY, I have a 68FB that only needs an engine and trans. but I am on the left coast. It has been sitting in my garage for 4 years with all the bodywork, paint, interior and wiring done. 3.77 backbraced rear end with a Detriot locker and Dutchman axles. I have some pictures of the car here, but since they were taken, I have removed the big block and C6 for another project.
Ron
http://www.rfedd.bigstep.com/generic.html?pid=13