I really like the 3.09 low model. But AFAIK that ratio only came in the Early As with the trunion drive shaft. So then you have to convert it to a slip-yoke type at extra cost.
Or you buy a burned up overdrive box and a standard mainshaft,and then shove all the early gears in there. Then you end up with a lightweight box,all aluminum, with ratios of 3.09-1.92-1.40-1.00 and splits of .62-.73-.71, and a bunch of junk parts. It weighs about 85 pounds now.
If the 360 is a lo-po, then you also have the overdrive option. And that goes well with your rear-end swap idea. But this trans is not really suited to a high-reving engine. It will be very similar to your A230, but with the added overdrive. It works very nicely with a 3.55 or 3.73. The ratios are 3.09-1.67-1.00-.73od and splits of .54-.60-73 You can see how far apart the gears are by the rather large splits.
Typically a guy would use the standard box with 2.66-1.91-1.39-1.00 with up to 3.91s for a really snappy city combo. But if hiway travel is important, than 3.55s would be the minimum.
So lets see what the roadgears would be with 3.73s, a middle-ground ratio, and the standard box.Multiplying it out I get
9.92-7.12-5.18-3.73 and this is a pretty good combo for a mid-level 360.If the cam is too big in the 360 for it's compression, then the bottom end will be soggy. This is where the 3.09 low would come in at 11.53 for 16% better take off.
So what would be the equivalent rear gear for the od box? Well that depends on where you hinge it.I like a minimum second gear in my 360 of 6.8ish; so that requires a 3.55 gear. Using that as the hinge point, I get 4.10s for the od box. And that will get you roadgears of
12.67-6.85-4.10-2.99od .. now compare that to the earlier standard 4-speed
9.92-7.12-5.18-3.73 or the deep low model
11.53-7.12-5.18-3.73
Notice the od box is lagging 4% in second and 21% in third,but gaining 28% in first over the standard box. Overdrive is strictly a cruiser gear, as I have found them to be easily broken.
Now how does this play out in real life?
Well the 12.67 low gear is more race-oriented, but to get the minimum second gear, you are stuck with it. Second gear is very nice. It will get you about 3000rpm@35mph, and if your 360 is close to stock, it will really peal-out. But if you put a big cam in the stock engine, the bottom will be soft and 6.85 will be a bit of a disappointment. But you are maxed out with the 4.10s on account of the granny low. So it becomes very important to not over-cam the 360. But that 6.85 second will get you 60mph at about 5100, which is why I call it the minimum gear. Hitting Third gear this early, with just 4.10 as your next road- gear will kindof suck. Say you took second out to 5500/66mph Well at the shift into third,the Rs will fall to 3360 and your race is over. This is why I call this a low-performance box. It's only good for two gears, and the 65=2420 is kindof nice, but third gear sucks.
I am very partial to the deep-low box and 3.55s.The roadgears are 10.97-6.82-4.97-3.55... It takes off like the standard box would with 4.12s, so first gear is a dump it and go deal. the 6.82 is a strong second, and third is close behind. With a hi-po engine now, the shift rpm might be say 6400, and the Rs will drop to 4600 NOT to 3360/lol, and she is staying on the pipe! But 65=2870 now,in top-gear, so that doesn't go over very well on long trips. So I got me a GVOD to drop it down to 2240.
Whatever you do; if you want a decent take off with 3.55s say, then stay away from the T/A box, with ratios of 2.47-1.77-1.34-1.00.. This is an excellent spread for it's intended application, but the 8.77 is a fairly soggy gear in anything but a stock 360, or a hi-compression small-cammed 360.
The lesson here is to match the trans to your intended useage. Or
Build the engine powerband to work with the trans.
Happy HotRodding
