cost depends on how much u want done. you defintly want the bore machined to get the ridge removed, you can get the top surface of the block machined so its all the same height & better compression, you can get the crankshaft tunnels machined to fix twisting of the block but thats very x'y and i doubt youll notice the difference. I'm assuming your getting new cams so you dont have to worry about that but you can also get your crank machined to eliminate ovality and taper but if you can find a bigger crank maybe out of a rb30 or something along with longer and stronger con rods you wont get a longer stroke but youll get more mechanical advantage hence more power.