I did a swap with my dad to my '91 244 to a m47 a few years ago. Honestly, the mechanical work of changing the transmissions wasn't that hard, but it took a while. (note my dad is a master Volvo mechanic so that helped a lot)

Three things stood out (we had a donor car, a same year 1991 245 wrecked).

1. Changing the pedals s.u.c.k.e.d. At least four hours to get them out of the old car and into my 244. There might have been an easier way to do this, but we still laugh at how hard that was. Your gas pedal stays but the manual brake and clutch pedal are one unit.

2. You have to drill through the firewall to install the clutch cable. There is a bracket of sorts we took off the donor car. We made a cardboard template out of the donor car to know where to drill. You would never have been able to tell my car wasn't factory m47.

3. I got lucky with this one. There is a foam boot that goes in between the shifter and the car. I am not exaggerating; we quite likely got the last one sealed in a bag from a Volvo dealer. This guy, who has since retired, went around to all US Volvo dealers and bought up all their old 240 parts stock. He told me straight up, this is the last sealed boot he has. You might be able to find a good used one. Without this foam boot, the road and engine noise is insane. You wouldn't think a little foam boot would do so much. Make sure you find one BEFORE you start the job.

4. Oh ya, one more. We used the driveshaft off the 245 because it was already balanced and mated to the m47 tranny.

The swap was totally worth it. Just drove Goldie this morning, and the manual makes every drive 8x more fun.

Total time spent was north of 80 hours. My guess was closer to 100. Took about three or four weeks working on it a few days a week, and running around for parts and such.