I have a T9 in my 1965 122S.

It is hooked up to a Ford Zetec engine (please note: I bought the car with the engine and transmission already swapped in, so I don't know all the details, although I have been studying the work done so I can make it a reliable daily driver), so I can't speak for the whole conversion, but it has a hydraulic clutch setup using the stock Volvo master cylinder; I imagine setup with a cable would be even easier for the later years.

As for the fit, the front of the transmission is very close to where the transmission was stock. The tunnel is not a problem as far as fit, but the shifter comes out about a foot behind the stock shifter. It's in front of the seats so it's actually a decent spot, but you'll need to cut a hole for it and fill the old hole. With a little carpet work, it looks real good.

The fellow who did the work on mine used the stock Volvo shifter, cut and welded to the stump of the stock T9 shifter. I may switch, or at least bend the lever to meet my hand as it's still a bit forward of the most comfortable spot!

Anyway, there's my 2 cents. I know it's not super helpful, but I guess I'm saying it does fit and can be made to look "right".

As for shifting, I've driven several Volvos and the T9 definitely doesn't feel as unbreakable as an old M40 or M41, but it seems less "clunky" and the ratios are pretty good (I still have the stock 1965 rear axle with the 4.1:1 ratio; I think with my 135 or so hp I may try to change to a 3.7 or 3.5 to 1 ratio if I can find an easy way to do so...).

Also, it's apples to oranges, but with the Ford engine/T9 combo I'm getting mid to high 30s for MPG in my first 3000 miles with the car, and I've got a lot of tuning to do yet. With a better rear axle I bet I can hit 40mpg and still have a fun car to drive...

Ben