My 1994 Mitsubishi 3000GT spins real quick but will not start

pop the cap and watch the rotor turn...if it ain't turnin' when the key is turned, bessie's gonna be in the car hospital for a little while~

...okay you've got a belt~

if this is the Single overhead cam...we will probably put a new belt and tensioner in without any interference concerns....but if it's a DOHC there is a definite possibility that this one is JUNK and will need new heads and valves~

As judge stated above if it is the dohc 3L V6. Do a compression check. You should have any where from 150psi to 200psi per cylinder. Sounds like your timing belt has either jumped time or broke. If that the case you probably have some bent valves. If when you do the compression check you have 0 psi on any of the cylinders that would mean that its valves are bent? These cars are known to do this. But don't fret. It not that hard of a job to remove the heads, have new valves and valve guide seals put in and put it all back together with a new timing chain and water pump. You just have to use caution putting new belt back on so that the timing is correct as to avoid bending the new valves the first time you try to start it back up.