1st gear in the V6 auto is very low, going from a stock 2.92 to a 3.45 would be more snappy off the line and that dude has it set up just right with good traction tyres as well and the LSD working well, 30m sure she could get going well.
The torque converter may be stalled higher into the power range as well.
If you do you homework you could work it all out, stall speed and 1st gear is what we are looking at hear. and top gear means nothing as top will be fine with even a 3.90, but 2ed and 3rd and 4th could be a let down in some ways.
I remember driving a V6 VE in 2ed it went to 110km/h and would only change back to 2ed at 90km/h so with a 3.45 or 3.70 would be crap in overtaking around the 100km/h using 3rd and lack of revs with what power you have she will be slower around there.
Your Torana would of went quicker with a Trimatic.
I had a mate with a VY SS and I the same he went and put 3.90 ratio in his because he towed a big trailer and 1st gear was way to high, now I drove his a lot and would I do it to mine, well no. but it was better for driving flat out because of the ratios, but we had plenty of drags and fanging on country roads and he only got the jump on me off the line 1st and 2ed but from 3rd I had him and from 210km/h I would just eat his bucket alive, we would come out on one part and he would be going for it as hard as he could and then it came to a straight open road and he would just back off totally because he knew that he was a cooked duck there, but spin some BS story, so I did my homework and figured out why and a ha ! the dog was out of the good power range and I was in the meat range of power and wind it out to 260km/h in 5th, 6th was useless.
Our utes were speed limited to 210km/h from factory but we removed that rubbish and his had MAF less tune and air snorkel and still could not out perform mine, but his was snappy due mainly to the air snorkel this gives more instant response, not talking about the lower gearing but we swapped the stock air box and then back to his direct type that goes straight forward out of the throttle body and opens up directly about 8in forward. them long stock types are crap for response. the next VZ he got he did the same but with a better bigger one, but it did over heat one day as it takes up to much in front of the radiator, but we were flat out as.
The stock VY manual SS ute was 3.45 diff.
The stock VZ manual SS ute was 3.45 diff but the SS sedan was 3.73, old mate chucked a fit about that as he said he would of been happy with the 3.73, so he had to change the ratio in this car as well and went for the 3.91 again. if anything the ute was the one that needed lower diff ratio. but when they brought out the VZ SS it had 250kw but they did not go as hard in reality as old mate came and gave me a run and my stock VY ate his, same gearing and many runs in 2ed 3rd 4th side by side on the UHF when to nail it and mine walked away every time.
I think even stock VS V6 could get the jump on the stock VS V8 off the line.
A mate had a worked 6cly Torana and V8's never had him off the line, but come after 400m that's were the V8's really shine with a street driven car. vs drag car.
Old box heads 202 Torana would flog any stock V8 from 180km/h on but to try keep it on the road was the problem as it just got air born floating about too much that you had to back off.