help with 73 340

hey guys, i am picking up a 73 340 duster that is the original engine in it. i am wondering all the differences in the enge compared to the older year 340's i know it has lower compression and smaller valves.
are the exaust manifolds the better flowing ones? same as the older 340's? i beleive that the heads have smaller valves, but what can i do to them to flow like the x heads? do the 73 heads hive big ports like the x or j heads?
what would i need to buy to have the h.p of like a 71 engine? pistons? which ones? heads? which ones? exaust manifolds? or the 73 ones ok? should i go with a bigger cam?
how about i aske a little differently. what are good choices to get this engine to be able to be driven every day, and still push 400 horepower? without nitrous or stroking it?
thanks for all the help guys
here are a few other questions..... a 73 340 duster came factory with a 904 or 727? 8 3/4? cause the rear in the car now is not a 8 3/4