Highest I can think of that I know the exact number of in a DSM on OEM 5 speed gears is 1017whp. I am pretty certain Shepherd made more, however I don't have any solid data to back that up.

I know AMS is making 1100+ in their Evo on stock gears as well. The rear end does not really have a solid limit, I only know of 2 ever broken due to power, one in the 1000whp range and one in the 1200whp range. OEM front axles hold pretty much anything and OEM the rear "bars" become iffy around 700whp, however at this point suspension and tire will go a long ways in preservation of parts.