i recently over hauled (not quite rebuilt) my 3.5 v8 and the amount of choice and upgrades are mind boggling.
the engine i had was good on compression and bores crank etc so left them alone.
after some advice i opted for a 3.9 cam, true roller timing chain and sprokets, rhodes bleed down lifters, new pushrods and steel rocker shafts and rockers.
all in i spent over 500 quid very easily.
it would all be down to taste how deep your pockest are and how far gone your engine is.
the skys the limit really.