Detroit 14L DDEC 6 Turbo Upgrade BUT HUGE Problem

I am in the process of upgrading the turbo on my 2008 Cascadia with S60 DDEC 6 engine.

As luck would have it, I brought my truck into a great shop that let me stay in my truck overnight. They are installing 6 reman injectors and a new injector harness. The shop also found the source of my miss. The rocker arm for injector #3 broke off!

While in the shop, I looked around for the T6 divided gasket. CAT has one but then I compared it to my new center section, P/N 23537114 and see that the DDEC 6 used a squarish turbo flange while the older engines used a more rectangular T6 flange. 23535457 is the P/N for the turbo gasket for my DDEC 6. Here is what the T6 looks like compared to the tiny openings on my exhaust manifold.



BTW my EGR is disabled but I want to keep everything looking stock. The exhaust ports on the T6 are at least 50% bigger than my turbo openings so that alone is a reason to upgrade.

Then I checked out the DDEC 5 exhaust manifold and it looks like it has EGR and a T6 flange but the EGR opening is completely different.

Any ideas what to do? The DDEC 5 exhaust manifold uses slip joints while my manifold has flanges and a flexible collar.

So, will a DDEC 5 exhaust manifold bolt onto a DDEC 6 head?

Finally, my turbo is both water and oil cooled but the new turbo (a Garrett GT4708) is only oil cooled. Will that be a problem?