Elite Contributing Member
Join Date: Nov 2010
Location: Buffalo NY
Thanked 654 Times in 470 Posts
As you know, with compounds the atmospheric turbo is huge and you can use it to supplement the stock turbo which is usually small and only good enough to make 30-40psi on a 5.9L inline 6 revving to about 4k.
Though similar in displacement, our 6.1L will rev higher, much higher. So the MAP will vary depending on lb/min and psi. Reduce the PSI but increase the amount of air needed due to the rpm (not displacement). Location of the turbo will also play a role. The a/r of the turbo will vary depending on location among other things. If you're only looking for 6psi, go Vortech or Procharger or Maggie. The work is already done and there is still room to grow. 76mm is popular, but I'm pretty sure a 72 would be in its comfort zone on a stock motor at low boost. Harry is running a 94mm on a 6.1 but its built up (to put it mildly) and doesn't spool very well, but it makes 1000+ wheel when it does light.
If you have an assortment of turbos, look at their maps online and see if they will work.