Need some Turbo help

I have an Iroc that I am going to be turboing here soon, and Im not sure what I should get. I have been looking into getting a Holset turbo from a Cummins, but then I heard that when you go with a turbo from a diesel then you run into the issue of losing power as your RPM's increase. I am looking to get all around best power out of a turbo. I heard that with a diesel turbo you get better innitial power, but you lose it the faster you go. Anybody know about that? Also, I am looking at what sizes to get and I think I want a 60mm, I am wanting to run about 8-10 max PSI. It is going to be a front mount intercooled. If anyone has any info on this diesel turbo vs non diesel turbo issue let me know, or if you have any suggestions on what you think would be the best set up for me. Thanks for the help.