Here you go guys. I put the 4 x most common aussie 4spd ratio sets in plus the 2 x common Supra boxes.
The lines below show each diff ratio, line next to the diff ratio is 1st, line below is top (4th or 5th).
So looking at the 3.36 diff with M21 (which is standard for 308 Sandman) 1st geat is 8.53:1, top is 3.36. By putting an M20 box in it and a 2.78:1 diff, 1st gear is all but the same and top gear becomes 2.78:1. This is basically the same top gear as fitting a W55 or W57 into the same vehicle leaving the 3.36:1. By using an M22 with a 2.6:1 you get a 1st gear slightly lower than an M20 with a 3.08 diff (standard behind 253 in HQ-HJ) but top gear at 2.6 is the same as putting a 5spd with the 3.08 diff.

M21 M20 M22 XU-1 W55 W57
1st 2.54 3.05 3.74 2.54 3.566 3.285
2nd 1.83 2.19 2.68 1.83 2.056 1.894
3rd 1.38 1.51 1.68 1.25 1.384 1.275
4th 1 1 1 1 1 1
5th 0.85 0.861

3.55 9.017 10.8275 13.277 9.017 12.6593 11.66175 1st
3.55 3.55 3.55 3.55 3.0175 3.05655 top
3.36 8.5344 10.248 12.5664 8.5344 11.98176 11.0376
3.36 3.36 3.36 3.36 2.856 2.89296
3.08 7.8232 9.394 11.5192 7.8232 10.98328 10.1178
3.08 3.08 3.08 3.08 2.618 2.65188
2.78 7.0612 8.479 10.3972 7.0612 9.91348 9.1323
2.78 2.78 2.78 2.78 2.363 2.39358
2.6 6.604 7.93 9.724 6.604 9.2716 8.541
2.6 2.6 2.6 2.6 2.21 2.2386


I'm not suggesting this is an ideal setup, especially lugging around town in 4th gear at 50kM/h. But what it is good for is for a weekend cruiser style van, taken to car shows etc but not driven much otherwise. Especially for a stock 308. Aussie 4spds are not super strong and can be broken. But if they do break under normal use it is usually because they are worn, not because they are weak. When these things were/are new they will handle decent power. All new bits can be bought for them now.

Bugger, doesn't post properly. How do attach a file?