The 340 is weak on the propshaft, you'll need a donor live rear axle and front mount gear box, requiring extensive chassis mods. A 360 can use a B2xx turbo from the bigger Volvos, they start at 165bhp, 200 with a bleed valve and standard parts. The 360 drive can take around 300bhp at a push.

A 340 ...

What's the point for only 170bhp? It's a whole heap of work. You'd be better off fitting a Renault F7R using B172 (1.7) conversion parts, but chances are it'll eat propshafts. Been covered many times, have a search around the forum.

If you plan on that kind of power, better to start with a 360 ...

I have recently developed a fondness for the 340, and have found a rather beaten one near me for 400 quid. I do intend to buy it, but I'm concerned about the lack of power. I would also like to try to swap in a V6 or V8, mainly for the noise. I was to take this car to the Santa Pod drag strip. Now ...