Eddy heads in my opinion are a lil too big for your 390, I would actually use a 302 head that has been worked over by a good cylinder head guy. You wouldnt lose compression that much with the 302 heads as you would with the Eddys either, only downfalls are its an iron cylinder head and compression would be limited to 10-11 to 1 depending on cam choice and such. Good luck with your build, I wanted to do one but got 2 360s instead haha.