take the belt off and make sure the valves are open and turn it over slowly and bring the piston to the top and see if it touches the valve but the easiest way is to find a service manual and see if it has an interferance engine
Ar you SURE it is a broken timing BELT? Have you seen a broken timing BELT and that is the reason it will not start?
(2.8 V6) ? IS it the SOHC or the DOHC engine?? ALL you stated is 6 cylinder!!!
I think one has a timing CHAIN.