Currently in my 85 SE Ltd convertible, I am using the 12AT box with 3.622, 2.186, 1.419, 1.000, 0.791 ratios with a 3.909 rear.

As spares are difficult to obtain, what is the best replacement box for around 220rwhp?

 

TII box for longevity. Haven't seen you post in a long time, was afraid you fell off the planet. I don't know if the 12AT box was any different/stronger than the other FB ones. We didn't get them.

 

Rotaries keep going round for ever! Not quite off the planet with 12 months on the Chinese/Afghan/ Mongalian border in minus 30C followed by 10 months New Guinea at 40C, no roads, but three types of lethal mosquito.

Now back in civilisation, the 12AT fired up first time. Thought I would buy 'SA22' a new gearbox for xmas.

The 12AT is stronger than the 12A with different ratios. 5th is .791 as against .825, giving a topspeed of 145mph which was not too bad for a stock Gen 1.

I agree going TII, but are there differences between models? The '87 5th was .762, later they were .756, then finally .719. Taking account of the rear drive difference that is equivalent to .684, which at 3,000rpm is a usable cruising gear taking account of gas price hikes in the past two years. From memory, SA22 gets around 140rwhp at those revs with the turbo spinning nicely.