Not quite right, 275...
The B-body cars of 1964 were sold with the 383s, the 413s and the 426 hemi... but the availability of these is not the be-all end-all of it.
First, the 318 Polyspherical combustion chamber (known variously as the 'Wide Block' etc in the USA) is what we have in the car and it's readily available. To buy a 426 hemi, for instance, would more than double the cost of putting the car together. The 413 is similarly hard to find in Australia, so you would most likely have to import two of them. One to build up, one for readily available spares.
Apart from that, Ben is convinced that the 318 Poly will deliver the goods... 450bhp or better when bored out to the easily attained 330ci (or thereabouts). It has good strong components in it and no real deficiencies, and there is some local experience with hotrodding them.
In the US they didn't get much attention because there were the big blocks in large numbers...
But even so, Gary Pavlovich and others think they are underrated and believes they can deliver good reliable horsepower. Ben has even got a book from the States about them that reveals a lot about their capabilities and underlines his basic belief in the type.
Now, there is the issue of weight. Even if it's only 100lbs difference between the 318 and the big block, it's a lot of front end weight to stop and turn on our (mostly very twisty) circuits.
And, of course, there's the limitation of 6" road type radial tyres. Having 600hp might be fine, but getting it to the ground through that rubber is a different issue.
Just to reiterate the engine rules, ray b...
3.1 ENGINE: The original type of cylinder block and crankcase must be employed. the bore may be varied and/or the stroke reduced provided that the swept volume of the engine remains within the same cubic capacity class as that within which the engine came as supplied by the manufacturer.
The original type of cylinder-head casting must be employed. the cylinder-head may be modified provided that such modification is effected only by removal of metal.
A dry sump is not permitted unless fitted as original equipment on the make and model of the vehicle of the period.
So we can go the rat on the engine other than stroking it, pretty much, but we must retain the original heads and block without adding metal to them. Any manifolds, any pistons, any rods and any cam at all. Valvegear is totally free...
Ben's plan is to use some good forged pistons in a 4" bore, a cam that gives good power up to about 6,500rpm, probably Manley valves. He's not going to rev it right out to the 7,600rpm that it should be okay to run because he wants two things... it will be used on the street occasionally, so it needs some flexibility, and he wants to build an engine that lasts 10,000 miles without a problem or a teardown.
One reason Ben is building this car, ray, is that he's a bit of a Chrysler fancier. Additionally, nobody else will build a Dodge, whereas there has been a Chevy or two.
In fact, the Chevy of the same model is heavier and has smaller brakes... this was the era in which Chrysler misread the market and were under the impression that Chevrolet were downsizing. So they built the monocoque body a little smaller than the other makers... and with the 11" x 3" front drums they were (I believe) 3/8" wider in the drum than Chevrolet had as their 'Police and Taxi' option.
I agree that a Chevy would be easier in some ways, but the Dodge has an absolutely bulletproof 4-speed while that era Chevy was still (IIRC) running the somewhat testy T10.
Another factor is that having a car that's different to the others will go a long way to ensuring that he gets invitations to some of the more 'desirable' race meetings.