|i'm going to say this now, you're not going to get a direct answer from any one person or place
specialtyZ can build great engines problem is, they have a huge backlog and i dont even know if and how long the wait is
epr has a lot of advertising and marketing and ive only seen a few builds with his motors but i haven't heard one terrible horror story about his work yet just lots of skepticism
IPP has been building engines for years but he doesn't do his own machining but kyle has been at it forever so lots of knowledge there
z1 does motors too, their prices are high and i have no experience with their actual motor builds so no clue if it's worth it
those are the main options, there are other people that may or maynot build you a motor. if you're looking for a stock refresh maybe buy one from a vendor that sells them with a good warranty?
there is legitimately no go to answer on this, also maybe find a place that is closer to you so if you have issues it won't cost an arm and leg to ship motor back. maybe a shop that you can even take a days road trip to, that may help in your decision.
Other than that, you're gonna get a lot of arguments for or against one place or another, you just asked the Coke vs Pepsi question and then you're gonna get some RC Cola responses