I am one that built a "hybrid" as some call it... true Holset, my comp blade is a HX40 - 6 blade "Pro" ( not the 7 blade super) 60/86, 49 trim with a pro style compressor cover..... my turbine blade is a HX35 - 10 blade 60/70, 84 trim.... and I am currently using a 14 cm turbine hsg....
I have built 3 turbo's and tested them over the last 8 months, this is so far the best for power, spool up, lower egt's.... for me anyway... all were HX40 base with different hot & cold side changes.... and I do have a intercooler and it really helps.. I can hit & hold 30psi when ever it's needed, but I rarely need that much towing grossing 20,000 lbs.....
Be aware there are some that call them "super or pro" , there are a few Holset part#'s that make them different and some folks aren't really sure what they have, the right part#'s are out there to be sure you get what is the real thing...
If you watch the auction sites you can get a good start to a great turbo if you take your time and do some research....
And these turbo's WILL " bark" if you boost them and get off the fuel quick like shifting quickly... I haven't broken a shaft yet, but I have seen it....