I-beam trolley

[TR4guyinVA@aol.com]

I'm slowly turning the large basement of my new house into a shop for my
cars. .  It has a long (25' or so) I beam supporting the floor above. . . it
is supported on ends by concrete block  and in the middle has a support
column.

I'd love to rig some sort of hoist on a rolling trolley to lift engines and
stuff like that.

Does anyone know of a place to look for such things 

or 

reasons not to do such a fool-hardy thing.?  


Thanks in advance