clk2 - hi there. I had the same issue when I built my car and specc'd the engine. In the end, I stayed with the 408 stroker, for the following reason - to get to 427, I understand that the piston pin ends up so high in the piston, that the
oil control rings have to bridge the pin area, leading to poorer
oil control.
Also, rod ratio is getting fairly poor on the 427 stroker.
Wether these are real issues for engines like ours, that rarely see very high mileages, I am unsure, but my personal decision was to stick with the 408 (4" stroke, 4.03" bore, 6.2" rod length).
you will need some good flowing heads to feed that stroker - I used Edelbrock Vic jrs, sure that other folks will have their own favourites. Were I building it now, I might look at the AFR heads.
Because of height restrictions, I stayed with a performer rpm inlet manifold - this dual plane manifold actually gives my engine better low down torque than the Vic jr single plane item I was thinking about to begin with. Very streetable, but still kicks out 450+bhp. Starts to get breathless above 5500 because of
the inlet manifold. Makes wonderful induction noises through the 800cfm edelbrock carby.
I also used the Ford X303 roller cam.
HTH