It seems like its 50/50 in the mopar world, there are some really excellent vendors, and there are some I wish I never wasted the time calling.
When I was building my first 440, I called a certain mopar specific shop to ask how well one of their crate motors would work in my 4x4 with it's tire and gearing. I can't remember the exact words, but it was a long the lines of "buy it and find out, if it doesn't work that's your problem.". I never bought a single thing from that place for that build.
On the other side, got great service from Marsh, B3, Dr.Diff, Cab Burge.