"cold air intake" piping size

hey guys
i am considering putting a "cold air intake" on my duster
i would utilize a spectre air cleaner housing like this one
98648 - Spectre , Low Profile 14 In. OD x 5-13/32 H - 135 Degree Chromed

it would be much like the olds W30 ram air packages, with two aluminum intercooler style pipes going from the cowl to the air cleaner

now, my biggest question is on the proper size of those two pipes

the air cleaner has two four inch intakes, but it looks like i can only manage to hook up a 3 inch pipe to the cowl

will two 3 inch pipes be enough to feed a 420 HP 408 ?

and if i do have to choke it, where is the best place to go from 4 to 3 inches?