65 cuda 273 to 360 tranny hookup

I am about to swap my 273 for a 77 360, what type of issues might I encounter? Can I use my 360 converter 3500 or must Iuse the 273 2500? I have the 360 flex plate. Can the old (rebuilt) 904 handle the power diff of the 360--350 to 400 hp? Is the spline different? Thanks gents!!