Here's my 2 cents on the combo I built...
 

standard GenVI 502 block - what I had to start with
.25" stroker forged crank
deburred, smoothed forged GM 7/16" rods
forged SRP's milled to 9.5 CR
GM cast iron rect. port heads - 2.25" I , 1.88" E, ported, polished, gasket matched, chambers polished, valves unshrouded, 3 angle valve job
Dart single plane, ported, polished, gasket matched
950HP Holley
EMI exhaust with 4" SS risers
Crane 169741 cam (236/244 @ 0.050, .632 lift , 112 ls, 108 center)

600hp on dyno with 600 ft-lbs. Same as Cord, hp was still climbing @ 5500 rpm but I shut test down)

I know the rod/stroke ratio is about as bad as it gets, but thats what I started with on my budget:D

mcollinstn, I think you've got it right when you said:
"big power and lifespan"
How about a different approach. Move the torque range down as low as possible to keep rpm relatively low and give it a 7.4L lifespan.
-540 tall deck (4.375 stroke)
-Supercharger 5-7 psi by 4800rpm (roots type to keep price reasonable)
-Cam designed for max hp below 5000rpm.
-Heads? Does port size and velocity matter that much with a supercharger?

Just thinking how to maximize hp without giving up reliability. Anyone think this will work? Can you make 700hp below 5000rpm on a BBC motor?

My $0.02
Gary

4.375 stroke will give us a 496 or 557 with a 4.25 or 4.5 inch piston, 540 would require a custom piston size, 4.43 probably not the way to go, , nothig wrong with a 557 tho :D

ursus
I think the merc 540 (bulldog and 900SC) runs a tall deck with 4.375 stroke and 4.43 or 4.47 piston. Too lazy to do the math.
Gary

4.375 stroke with a 4.47 piston gives 550 cid
the 900 SC is indeed 4.38 stroke x 4.44 bore 542cid

ursus
540, 542 cid, whatever it takes.
What do you think about the low rpm supercharged motor idea? I liked your rod length thread and was surprised how little piston velocity was dependent on rod length.
I've always been under the impression that long rods were used on high rpm engines to increase piston dwell time near TDC. However, is there a dowside to longer rods in a low rpm engine. I posted the question in that thread if torque varied much with rod length given a constant force on the piston. ie, shorter rods result in more crankshaft torque at times during rotation. Got a program that wil graph that?
Gary

Cord,
What cyl. heads and how much more compression?I am building what I consider to be a conservative 540. Gen 6 std .deck block
Eagle 6.385 Rods L-19 rod bolts, Callies 4.250 Gen 5/6 style Crank (one piece rear main seal), Fluidamper,SRP 9.0 to 1 pistons.Crane 741 cam, Crane 16535 hyd .roller lifters (Use stock lifter guides) Canton oil pan,Victor JR intake port matched,Canfield 310cc.intake 123cc combustion chamber ,Bowl blended& port matched,Hard anodized alum cyl. heads Manley extreme duty inconal exhaust /severe duty 2.250 intakes.Holley Marine 850 cfm Double pumper carb ,Canton offshore pan. Harlan sharp 1.7 Rockers.Anyhow are engines are close .

Rob

Howabout this instead:

4.600 bore x 4.375 stroke = 581.66.......... Naturally aspirated

If you're gonna use one of better blocks go a bit bigger........ they are harder than others (4.625 max recommended bore)..usually unless you chuck something, you can just dust the bores & you're back in business.

Ok, here goes:

Block: Donovan Aluminum tall deck block (Just kidding - CNC bowtie block, or dart tall deck block)
Compression: 9.5:1
Crank - LA. or Lunati
Rods: 6.800, carillo, lunati, or LA
Pistons: Diamond custom pistons & pins
Heads - oval port big chiefs
Valves: Some really good ones
Cam: Crower...tell them the app, let em grind one.........most likely on a 112 c/l
Valvetrain - Jesel, T&D. or Crower
Intake: custom sheet metal
Carbs: a couple of 1150 tweaked dominators

..........Ok, now times that by 2, and................voila, I'm still runnin the little 355's in my scarab !

Ok, maybe a single dominator, like in this pic ?

http://www.rehermorrison.com/

Click on the 565

rws-I was told that they were bowties, but instead of the bowtie symbol over the exhaust port there is a winter symbol. The same snow flake that's on the 454mag winter's intake manifold. They were fully ported and bowl blended. It's the exhaust port that is absolutly critical. The stock heads have a really crummy exhaust port.

I know that my engine has some H beam rods, but I don't recall the make. I also don't recall the compression ratio. I'd have to look on the build sheet for the number. I'll get back to you...