The number one issue with determining whether a bike should/could be converted is dropouts.
Typically you want horizontal dropouts so that you will be able to have some room to adjust chain tension. If you have vertical dropouts(which I expect you do) The easiest, yet rather expensive option is the ENO eccentric hub.
You could also get your chain close, and then use half links to make the vertical dropouts work in a fixed gear setup.
The fusion will have vertical dropouts. If you're sure you won't ride it anymore, you could get some pretty good money for it and buy a complete fixed gear/track bike. Or, sell some things, buy an old road frameset, and convert.
Originally Posted by CardiacKid
I explained that he could never pay me enough cash for the amount of work I had put into that bike and the only way to compensate me for it was to ride the hell out of it.