paul, i'm savin for my 557 now, got the block bored already and its on the stand....what kinda power do you think a mild roller(650-680 lift maybe) cammed 557 with d3's will make? i've already ported and intalled bigger ss valves in the heads, just not gonna be able to swing nice heads this yr. after building the short block.will be runnin a victor with dominator...roller cam swap is expensive once you factor in springs, lifters, pushrods, and cam all together...ya got any used roller cams and lifters layin around.
I'd strongly recommend porting the intake side as well as the exhaust, if using D3's on a 557, even consider a CJ port match on the intake and use of a CJ intake ported manifold...but the engine will run without that last part... Final power output will vary widely depending on final combination, but I venture to say that 700HP is possible under absolute MAX optimum conditions, but that far less power is likely under more realistic conditions.
If you want to run a really high lift roller cam in a motor that bombs around the lake all day long at 5000 rpm, plan on preventive maintenance that will go as far as pulling heads in the off season the touching up seats/valves, checking valve springs a few times per season, roller lifter replacement, etc. Better safe than suddenly $5000 in the hole, if you know what I mean. My parter has dozens of roller cams of his own to choose from; I need to inquire with him and also know more about your combo...personally, I'd opt for less lift cam in the 5000 rpm D3-headed motor...the exhaust doesn't flow any better over .600" or so lift. You can get around this with duration, especially in your applicaton.
LO