Has anyone here converted a c6 to toploader or even a t-5? Any & all help or suggestions appreciated.  

Might fish around over on fordfe.com - lots of info on  FE related things.  

Having owned a 67GT I can tell you it is one sweet ride with a Top Loader.  As for the t-5 the only advantage is the overdrive. However, it does not compair to a Good Shifting Top Loader, get yourself a Hurst Comp Plus shifter, and I like a CenterForce Clutch to handle all that torque.  A few years ago when I was in need of one Jasper (the engine people) had reasonable prices on Top Loaders. My thoughts are this if a good running 5.0 makes enough torque to stack up the gears in at T-5 what is a 390 going to do to it??  and I know the top Loader shifts better different but better.  Feel free to contact me direct if you want to talk about your project it really sounds like Fun to me.