A998 Trans in '66 Dart

The 999 ratios allow the next smaller rear end to be used for the same starter gear. This allows about 10% less cruise rpm for the same speed.

In the lightweight As, I don't see a point for the lower gears,except for the cruise advantage.

If you don't tub your car, you cannot run a big enough tire to not be spinning with 400hp, for most of the Eighth or more anyway, so I wouldn't worry about the difference in the trans ratios.
But, in your case, yeah, the power band might be a ill narrow 7
The transmission has a PN stamped on the panrail that someone here can look up for you. I have heard that some to most of them have the model number cast on the top of the bellhouse.
ict
I have heard it said on FABO that modern TCs don't suffer those overheating woes. But I imagine if the stall is very much higher than the cruise, I would still run a cooler.

The thing is, that with 400hp, in a stock body, for a streeter, I see no good reason to run race gears, nor a very high stall., because the engine is way overkill anyway and is gonna commence spinning the skinny donuts almost right out of the gate.
Oh wait, you said 331 cubes. To get 400 from just 331 means that you are running a very big cam and a Lotta compression, which sorta forces you to run those big rear gears, so, ok, I get it. And the bottom end will be soft, forcing you to run a big TC, I get that too. So then the A999 is making sense. But with a 3000/3500 stall you are still gonna blow the launch with whatever skinny tires you manage to fit in the back. So then, you can get a loc-up in those A999s
But in your case the power band might be a lil narrow to properly pull those A999 ratios,.IDK., unless you do in fact run a very high stall. But again, I just don't get why you would build a combo like that and then put skinny tires on it.
What am I missing



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