Slant Six Solid Roller Camshaft

when you mention 290+ duration, is that @.050 or advertized?

And something to think about,
Since you are planning around a roller cam, the open and close ramp angles will be a lot steeper.
The roller will open and close the valve faster, the engine will see the larger valve lift values sooner and longer (depending upon how the lobe is profiled) so with a roller you may not need to plug in more duration compared to a solid lifter can to get the effect of more duration.