What year, and what else do you want to do for the setup???
I used to offer DIY kits for head porting, where I would do 1 cylinder and
then it could be copied. Maybe you can find that somewhere for intakes.
If you decide to DIY it I will give you advice, I did most of this stuff before
anyone else ever thought about it, while Morana was playing with carburetors
I did the world's first SPI intakes in april, 1999
PS: bigpomp is right for SINGLEPORT, but SPI street combos
run really well on a 3.8 with the heads unported, intakes ported,
and a cam and tune. Head porting is good, but for most folks
it is a bit expensive and the gains are minimal, compared to the rest.
STOCK SPI heads flow really well, it is pretty easy to overport them
for a 3.8 and it is done all the time.