I would stay with the same pistons and just replace the rods. I would use 6.535" rods which will give you a rod angle of 1.54(rod length/stroke) and will leave the piston about .020 below the deck. A rod angle above 1.5 is just fine. I would only replace the pistons if the block needs to be bored. Hope this helps.
Eddie

ss,
I did not see any mention in your original post whether you actually measured how far the piston was down in the bore at TDC ?? If it actually was .150" down in the cylinder, then ignore the rest of this

If however it was closer to the top of the bore you really need to find out why. Only reason I am saying this is that I have seen some guys do some real crazy things like .... cut .150" off the block deck for some reason ????
Or maybe the crank started out life as 4.250 stroke but has been changed ?

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Bill im goning to yank the other engine apart and check it thoughly. I talked to gelnner and he said sine the work that has to go into it, might as well dump a set of 4.5 cranks and make them 572's

you should of called back jim reid didn't he build those motors you said when you bought the boat you picked up the motor from him a part. I would think jim would know whats in there and his prices are good. in 10yrs of running his motors I had one bad vavle that suck and bent and had a 12yr old rocker stud break thats it. I hope it will be fine sitting as my back up to Dean gellners 572. maybe get a new intake