Hello! 
So i have w201 and om605 engine on it. Thats it for the moment  
Also have as spare parts w210 om606td, w202 om605 td and w203 om611 with 716.603. 
So the question IS should i leave for my self this gearbox for my build? Mby any other suspension and drivetrain from my donor cars should i save? Any experience are welcome. 
Forgot to say for first time im going to have mechanical pump with 6 mm from edc. The Goal is something about 250 hp and max fast spool.  Later mby im going to upgrade to max 300 hp. Thank you very much.

Any suggestions?

AFAIK the 716.60x (rated at 250Nm) is not that strong. May or may not handle 250hp, it depends more on the torque. It's better to get a 716.65x (rated at 370Nm and proven to handle ~400hp OM606). But IMO it's still stronger than a 5 speed.