I have the 54 cc 289 heads on my car now, I looked into getting them worked but for the price (about $700-900 depending on level you want) i spent another $300 and got a set of new 165 AFR's, they will flow better and weight 40 lbs less than the worked heads could come close to...my .02....
I spent money on getting my 289 4V heads reworked and did notice a difference, but i wish i would have just waited and saved my money to buy some aluminum heads.
Good move. But you should have those shaved to 54cc (max recommended on those heads, as I understand) to keep decent compression. You may also look at getting a used 302 rotating assembly (cheap, cheap!) for a nice bump in both compression and performance.