Volvo PV544 driveshaft / rear axle upgrade with power increase?

I am planning an engine upgrade in my 1964 Volvo PV544.  When complete, the car should make around 250 hp at 280 lb-ft of torque, and I'm trying to get an idea of how many of the original components I will have to replace to withstand the power increase.  I know the transmission will have to go, as the M40 would likely be pushed to the limit by my upgrade, but I couldn't find much info on the strength of the drivetrain as a whole.  Will I need to replace the driveshaft, differential, and/or rear axles to accommodate the power I'm aiming for?

Thanks in advance!

Run it until something breaks and then upgrade as needed. 

Seems like a good place for an 8.8 from a ranger. Do the trick where you narrow it with two stock short side axles.

After the transmission, the driveshaft will twist the ears off the yokes, followed by the rear end. At the very least, you need the drivetrain out of a 240 turbo. Best would be the shortened Explorer 8.8 and a custom 2 piece driveshaft with a T5 transmission which would give you the correct rear wheel bolt pattern 5x4.5". I guess I don't know if a 1 or 2 piece driveshaft is better.

My 164 6 cylinder engined 1800 wiped out its driveshaft on stock wheels with about 155 lb-ft while dropping the clutch once.