Yeah the T-5 bellhousing will bolt directly up to the 351C. I'm not 100% sure how the input shaft does though. It may fall short to be too long. Not sure on that one. I'd assume it'd be the same as the 351C shares the same trannies as the 289/302/351W. Remember, it uses a cable style clutch setup too.
You'll "lunch" a stock T-5 when behind a Cleveland if you drive it any more than an old lady would. I haven't heard of the kit techinspector1 was talking about and I'll have to look into it for mine as well. A Tremec should survive with no problems behind your Cleveland though. The newer the T5 the better the torque load it will handle, as a general rule. T he over the counter Motoprsports T-5 is a pretty good unit but I think you'll need more than that. It's rated haigher than any of the other factory produced units.