What they want ... I think
From the FedEx website:
"1500 hours total fixed-wing time as pilot-in command (PIC) or first officer (SIC) including a minimum
1000 hours PIC in fixed-wing jet, fixed wing multi-engine turbo-prop, or multi-engine recip over 20,000 LBGW or combination thereof.
Note: PIC for this purpose is defined as Captain/Aircraft Commander of record, not simply the sole manipulator of the controls.
Note: FedEx considers only pilot time in fixed wing aircraft toward minimum qualifications. This does not include simulator, helicopter, flight engineer, bombardier, navigator, RIO, EWO, WSO, NFO, or Special Crew."
So in your case the lim fac isn't the weight but the number of motors on the plane. ie any T44, C12, or KC130 time would count towards the 1000 hours, but T43 time would not. It is my observation that no matter what the stated mins are most majors are looking for roughly the same thing, whether they explicitly state it or not: 1000 hours QUALITY PIC. There are some minor differances in what quality means (SWA wants turbine, FedEx wants Jet or big, etc), but the basic idea doesn't seem to change: the person in charge of a complex/fast fixed wing aircraft. I guess there are enough cargo carriers still running big recips for FedEx to leave that opening for them, but for whatever reason they don't want caravan guys.
Also, referance this thread
http://forums.flightinfo.com/showthread.php?s=&threadid=2329 for another discussion.