High boost and on some trucks there would be fitment issues, IIRC evaporator will be too close to turbo GMCTD had to rework that when he put the 6.5 in his 84 3500 dually
It's pretty much all explained here.... http://www.thetruckstop.us/forum/showthread.php?t=22280
earlier 6.2's the manifold hits the injectors, If the truck has AC it will not clear and ex has to be fabbed ans well as other things. It "can" be done but certainly not "Bolt on". Higher cmpression is true but a 6.2 can run a turbo if kept at 7-8 PSI and egts under control.