Looking for more HP from a 360

I,m looking to get more HP from my 360 with X heads.Here,s what I have..
77 360
crank is .10 over
pistons .30 over
Xheads with mild P&P
484 cam
rpm air-gap intake with holley 750v.s
stock dizzy with MSD 6al
Spitfire headers to 2 1/2 exhaust
tranny is 904,trans-go 2 kit,2500 stall
8 3/4 3.91,s

I,d like to get more HP,so do I get my heads fully done or Eddy alumi.?New bottomend?This is for my 66 Dart mostly strip,but the odd show.This winter it will be getting a minitub,spring reloc. kit and maybe a cage.Now I,ve read about 9 different builds with stock bottomend up to 500hp,so can I use this bottomend and have my X heads completely done and what cam for max.hp?Any advise will be taken in to consideration for a new engine build.Thanks