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Chris, after reading your post here's the things that come quickly to mind;

Bearings: I have used Clevite 77 bearings my entire life. They're tough bearings. I don't know anything about King bearings.

Compression ratio: let the cam grinder specify the compression ratio

Cam specs: Let a competent cam grinder spec your camshaft. You should plan on a bit more lift, on the order of 0.630" to 0.650". Off the shelf cams that fit the Windsor block will not work with this combination, a custom ground cam will be a must, but don't stress, you'll find the difference in price is not that much. (Even with a Cleveland block, off the shelf cams are designed around the 4V heads, to get the most out of the high velocity CHI 3V heads you would still need a custom ground cam) Another benefit, the high velocity ports of the CHI head will allow you to run more duration without penalty in drive-ability.

Valve springs: your cam grinder will want to spec your springs for you too. Cranes hydraulic roller lifters allow more rpm than the Comp Cams lifters (Comp uses Ford oem style lifters). If you're going to run Comp Cams lifters, beehive valve springs would be a waste of money. Consider the Crane lifters & beehive springs as a necessary pairing. However, for red-lines below 7000 rpm I doubt you need the beehive springs. Your cam grinder should have final say on this issue.

Pistons & Rods: buy the crank, pistons & rods as a kit from the same supplier. Just like the compression ratio & cam specs, let the crank kit supplier decide what connecting rod length & ring package to pair up. Scat would be my recommendation. Choose a kit supplier who will custom grind the dishes in the piston domes to match the shape of the CHI combustion chamber. I like floating pins for the ease of assembly they allow. There are other options here for a supplier of your crank kit. I could recommend an engine builder for you that would make one stop shopping for your crank kit, head work, cam grinding, etc ...

Intake system: CHI makes a manifold for this application (3V heads on 9.5 Windsor block). Their manifold will work best with their heads, period. Top it with a 750 cfm Holley...

By the way, I don't remember Kelly C casting an IR manifold for the CHI heads, especially on a Widsor block. The CHI 3V intake ports are 2V sized but raised approximately 3/8" vertically from the standard 2V location.

Rocker arms: 1.73 to 1 is the stock Cleveland ratio. Crower's enduro rocker arms are available in 1.73 ratio, however, they are also available in 1.75 ratio, so I would recommend the 1.75 rockers. Why? Because they allow more lift without any more duration. Gives your cam grinder more options with the cam lobes. For a bit more money, the Yella Terra rocker arms would be a step up in valve train stability.

Misc: you'll want 3/8" push rods (or heavy wall 5/16 push rods), heavy duty oil pump drive shaft, double pin the distributor drive gear, high pressure oil pump relief spring, and a high pressure oil filter like the Fram HP1. The Dart block is good stuff, good choice. If available, install a main cap girdle, it controls main cap squirm much better than four bolt mains alone. 600 bhp is a lot of bhp, you need to build all the strength into this assembly possible. Rollmaster timing chain, Romac balancer. Before final assembly have the reciprocating assembly dynamically balanced.

With a goal of 600 bhp & a displacement of 427 cubic inches, don't be surprised if your cam grinder recommends some head porting.

To achieve 600 bhp at 6500 rpm your motor will have to be making 484 ft/lbs of torque at that rpm. This should give you an impression that your powerband must be skewed towards upper rpm. If you will be operating your Pantera a lot on the street & on the track only once per year, I would advise you to build a "street" motor, the motor you propose is not a street motor. A street motor gets on the pipe not too far above idle. In my opinion, the thing that wins stop light drag races is a low rpm powerband. Drag racers side step the clutch at 4000+ rpm, they don't need low rpm powerbands. But at a stoplight, you'll leave the line just above idle. So my advice is to build for as much torque as possible over as wide of a powerband as possible and let peak bhp numbers fall where they will. That powerband should commence between 1500 & 2000 rpm. A car with a street friendly powerband is less of a chore to drive, easier to relax and enjoy the car & the trip.

That's just my advice, I respect the choices you make because I realize we all have different ideas about what OUR ideal Pantera should be.

Your friend on the DTBB, George