The only thing that may not be obvious is that the little plastic ring with a pointer has to be put on with the pointer at the line to the right of the "ramp" cast into the tensioner body (that is, past the "short" end).
Install tensioner and rod, pulleys, and belt. Leave 19mm main bolt just snug (the rod rotates the inner part, not the outer part and it has to move), then tighten the adjuster until the "pointer" moves to the top part of the "ramp" cast on the tensioner.
Tighten 19mm bolt to 55ft/lbs, I think.
If you have the bolt tight when you attempt to tension the belt, you will break the tensioner rod again.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!