I scoped out the Helion site: Hellion Power Systems - Fox Body Turbo Kit
Pay them a visit and drop them an email at the "Contact US" port.
Off hand, I'd go with 2 66's for the 351 (Hellion offers a single turbo kit with a 66, and a 76 as the larger upgrade), but that might be overkill since you aren't shooting for really high boost. The smaller turbos sold on Ebay might well be fine for you. I'd do some soul searching before you start and determine what your rwhp goals really are.
Will 400rwhp be enough? 500? 600? More? The hp goal will drive all the other choices you are looking at right now. 20psi of turbo boost on a built 351 will make LOTS of power (probably at least 600hp, and perhaps a great deal more depending on how all the parts come together) if you feed it with lots of fuel. If the car is to be a dedicated race car, that sort of situation can produce upwards of 800hp without too much trouble, or a 1000.
In general, the smaller the turbo the quicker it spools up (though this is also affected by the turbo's design, too - the newest designs feature turbines with superior abilities). This helps cut down on the dreaded "turbo lag", and makes tuning easier (and the car more pleasant to drive). The tradeoff is the ultimate horsepower made by the motor. Whatever you do, pay attention to feeding the motor enough fuel - fuel starvation and running lean will detonate your plans in a hurry! Make sure you have a good gauge on the fuel and the ability to regulate the fuel supply, as well as a return system and rails that can handle the results.
You should also consider selecting turbos that use beefy, ball bearing construction. The cheaper ones WILL fail under load, sooner or later.
I'd recommend using steel Cometic head gaskets (they will withstand more boost - using a thick conventional gasket or two will just invite leaks and blow-outs, particularly on a boosted motor). If you need to drop compression (9:1 might still be a bit high - 8.5 or 8.6:1 would be better), consider changing your pistons or cutting yours the appropriate amount.
DO NOT go cheap on the blow off valves! Bigger is better, and creating a "runaway" situation with a turbo is a recipe for disaster - so pay the nickel and get top quality blow off valves BIGGER than you think you will need.
HP has some nice turbo kits too, and Modular PowerHouse
installs these on Mustangs all the time.
I'm thinking you are still needing to do more research with the true experts (vs I-know-just-enough-to-get-you-in-trouble idiots like me), so start emailing or calling up those companies who sell the good kits. They should be able to tell you what they would sell you in a kit, and the parts list would be really helpful.
Finally, DO get an experienced tech with a good dyno to tune the results when you are done (even if you get one of the kits and the handheld tuner that comes with it). JUST to make sure you aren't about to blow the thing up running too lean!
well thats what i'm sayin is that my familly owns a machine shop, thats what i do for work. i was planning on taking the time to fabricate all the pipe and brackets and everything else. i could even make the manifolds if i took the time to do it i just thought i would save some time by getting the manifolds in the kit. i hear what you're sayin about don't believe everything you read. i really don't have much experiance with turbos, but thats definitely the way i want to go. you sound like you have a lot of experiance so what kind of turbo do you think i should run? what i'm going to build it on is a 351 with a forged rotating assembly with plasma-moly rings. i'm not saying i want to run 50 psi. boost all the time but i think it will handle 15 or 20. as far as the cylinder heads i have a set of GT40P's that we CNC ported and with a little thicker head gasket i believe i can get the compression down under 9.0:1. i just want to do something different with this motor because there are SO many people have supercharged windsors, and i know there are a lot of turbos out there but not where i live. i've had a couple of supercharged motors before and they were great don't get me wrong but i wanna do something different this time and i really can't spend 5 grand on it. even if you know where i can get a kit that just comes with turbos and an intercooler, waste gates, blow off valves could you let me know because i want to make the rest myself. thanks