Everything is more expensive for the 340. A 318 or 360 would be cheaper to hit your HP range. I believe the K member will need swapped for the 340, but I'm not an expert.
Also, will your tranny and rear handle the extra HP/TQ?
I've done a little bit of reading on the subject, I believe the 340 bolts right in with a some modification to the passenger side mount... I have the 4 speed a833, and a 8 3/4 rear on the way...
I came across a 340 for a good price, and like the idea of a hi revving v8... Keeping it for sure.