Upgrade SYS on Custom Rom?

[emd2009]

I am using a custom rom that I downloaded from here, and I was wondering how I would go about upgrading the windows mobile build to a newer one. I want to keep everything the same, just a newer build of Windows 6.5. The chief has moved onto an Evo and therefore I want to keep it updated for my own personal use. I know some kitchens provide the option of dumping a rom, but I have not been able to boot past the touch pro 2 black screen.