I just want to put my 2cents in.
In your case, with 650 hp I'm assuming is normally aspirated, I'd contemplate the automatic, seriously. I think your life will just be so much easier.
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As for automatics;
If you don't know it;
The convertor acts like a two-speed autoshift by itself.
From a deadstop, it might have a ratio of 1.8 or more. When you invert that so you can compare it to your other transmission gears, 1/1.8= .56
This compares nicely to the Mopar 727 ratio splits of, .59 and .69. So then, from a dead stop it is acting exactly like another gear in the main box, and the splits are .56 going towards .59, then.69
But, the convertor begins to hydraulically alter it's ratio towards 1:1 just as soon as the car gets moving. At top speed, that ratio may be approaching 1.1 or less.
If you have a Lock-Up on it, that will finalize to 1:1, direct-drive. Thus the factory 727, will perform like as if it had 4.5 gears, compared to the A833, at just 4 gears.
This is why, factory cars almost always had 3.55s to the manual trans, compared to 3.23s for the automatics, cuz the manuals need the 10% more take-off torque multiplication, to keep up with the autos, in that very early stage of acceleration. Once the car is moving towards the top of first gear, the edge goes to the manual, with it's tighter splits and extra gear.
But
1) IMO, for a streeter, none of this makes a big deal, until you eliminate tirespin. and,
2) How much of the 650hp is on motor? and
how slow can you honestly idle that engine?
IMO, notta chance would I run a manual with that much normally-aspirated power, the reason being, is that 650 takes a heckuva cam, inferring a higher idle, and so, how do you drive slow.
3) lets say the lowest rpm that it will idle smoothly enough to pull itself is 900rpm. In 2.66 First gear, with 3.23s and 28s this comes to ~9mph..
4) whereas, to get that down to 4mph, will take at least twice as much rear-gear, say 7.00s, and/or a lower first gear, and/or a lower idle-speed. and Well, if it was possible to run a 7.00 rear gear, you'd need another gear or two, at the other end, to cruise with. Whereas
5) with an automatic and a higher stall, you can idle at any walking speed, thus
6) IMHO, this vehicle is begging for a 4-speed auto. lock-up optional.
7) These are my opinions.
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as to a manual trans
Having said that,
the combination of Mopar Commando(3.09low), together with, a GVod, and at least 4.30s is a good option for this , if the engine has a good amount of low-rpm torque.
If you can get the engine to idle down to 650; with 4.30s and 28s, that translates to a tick over 4mph; and 65=~2600rpm
Now, if your engine on motor is say 450 hp, then you might get her down to 575/600 idle in gear. Ok then, 600 is ~ 3.75 mph, and say 575 is ~3.6mph........... now you can parade that beast.
And yes, I suppose you could run the Passon od or the Mopar od; however only the Mopar will get you the 3.09 low. So to get that 16% lower first gear with the Passon, she'll have to run 5.13s for an overall First Roadgear of 13.64, compared to the Mopar with 4.30s at 13.29
This presents a cruise rpm dilemma.
With 5.13s and .80 od, the Passon will run 65=3200, versus;
the Mopar with 4.30s and .73 od, will run ~2450
However, the Mopar OD gear is rather fragile, and I can practically guarantee you that unless you put a lock-out on it, you will break it.
Therefor do I run the combination of Commando with the GVod, and, at one time, 5.28s/4.88s/4.30s, until I figured out how to get my idle speed down.
So now, I get the 3.09 low AND the .78od, and the very tight splits.
For you with 4.30s, and with 28s; this comes to
640rpm= 4mph, and 65mph =2600
And, at ~430 hp, I have not been able to break anything except clutch-discs, which are my chosen weak point.
So
if you're gonna run a manual trans, I humbly suggest the combination of Commando/4.30s, and, with the GVod if hiway driving is a concern.
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Before I sign off, I gotta mention that I use that GV as a gear-splitter, bypassing the GV shift module..
The commando ratios are
3.09-1.92-1.40-1.00-.78(GV).. with splits of; .62-.73-.72-.78
But I shift from third into od, then into 4od so my splits are actually;
.62-73-.78-.71od
Now
When splitting, I split the 1>2 , and then into od after second, so the ratios are;
3.09-2.41-1.92-1.50, and with 28s and 4.30s, that 1.50 ratio will get you 65=5040/6000=77mph,
and for me, 93mph in the Eighth comes at 6200 with 3.55s, lol.; that's one pull on the stick, and two lightning-quick electric shifts, with splits of; .78-.80-.78.
I mean, so there is that, lol.
BTW
If your meats are not 28s, then all rear mphs and rpms have to be adjust by whatever the percentage difference is, between 28 and whatever you actually have, for instance 32s would drop the rpms to .875, and the rear gear would have to increase by 1/.875= plus 14.3%..
If you need help, just ask; I got nothing better to do, cuz
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