Just browsing through this article http://www.racecar-engineering.com/n...e-regulations/
DTM and super gt (gt500) share technical regulations from 2014 onward, but differ in engine regulations. Article is a bit old so not sure what has changed.
Keep in mind that Super GT has two classes, gt500 and gt300. Just looking at the super gt site, it seems that the gt300 class is more akin to the gt classes of alms with multiple brands represented by the likes of a r8, gt3, Z4, gallardo, sls, f430 etc. Seems like an interesting series that looks to be competitive by glancing at the results.