Can I use a torque multiplier on the crank bolt?

[volvo 4 life]

I don't have access to a 3/4 inch torque wrench but I work at a Ford dealer that has a Rotunda 1/2 inch to 3/4 inch 5:1 torque multiplier. It seems to me that if I set my torque wrench to 70 ft. lbs it would end up being 350 ft lbs at the bolt so it should work fine right? What is the actual spec and what do you guys think? Thanks, I really want to get this belt done especially since I noticed there's a spot on the edge where it has just started to fray!