if it's just a daily driver with basic mods Im not sure if i would go with a Manifold.. you tend to lose low end power..
now if you plan on F/I or a big N/A build then there are options..
one is the top speed manifold- it takes forever to get and well expensive as well..and apparently some people had issues with fitment? im not sure its all second hand knowledge for me on that venue.. ive never messed with them-
finding a Ford Racing manifold that I've really only seen on zetecs not svt's.. so tbh im not sure if that would even work.. and also requires some work to make it fit correctly..
there is also Jim's / Nerps manifold that we are trying to get people to jump in so they make one last run. for SVT's you will need a bracket made for wiring which Corey (another member) can make for you..
overall you will need a tune if you do decide on getting a manifold.. that is a must..
few awesome tuners around here that can help you out.
Stock works just fine and there isn't anyone on the board who has enough N/A power to justify changing it.
The money you would spend on an I/M would be better used towards cams, expensive as they are.
Or if you want more RPM, oil pump gear and valve springs.
I have a SVT head with a Ford Racing Intake Manifold. The first gen manifold almost fits perfectly. Runners are about 1/16" off but can be ported to match. Also the alternator bracket needs to be slotted so the alternator moves down about 1/4".
And good luck finding one.