I have a thread on here from about 3 years ago on my HX35 setup - mine is completely custom fabbed (in stages mind you) and has worked well so far. I can run 55-60 pulling a 5-6% grade at 16k gross which is good enough for me. Top out at ~20 lb of boost.
Big thing is to have a realistic idea of what you want to do with it and work back from there.... seems like lots of folks spec their plans based more on the woo hoo look at my big ***** boost numbers than any real appraisal of what they want to truck to do. Seems like a dumb idea to me. My setup is based on reasonably achievable power gain for towing with reliability foremost, and it's been good thus far - somewhere around 25k miles now.
Are you planning to rebuild the motor? mI would want shaved pistons to go over about 10-12 psi. I decked mine 0.015" and had them ceramic coated - drops the cr to about 20.5 IIRC. I would probably go for 0.020" if I did it over again, since the ceramic coat adds a few back. I've had it in weather down to 20-30 and it's always started fine - can't really tell any difference starting between it with and without decking, though you might in really cold weather.
HX35 seems to be a pretty nice turbo to me, and is easy to get. It's the same T3 flange as the Banks and others, but is a bigger housing so I strongly suspect it wouldn't fit easily on a standard Banks/ATS setup. The downpipe flange (at least on mine, I think there's different variants) is close to a 3" v-band, but isn't.