big 'K' on the outside of the case, around the bellhousing area....
The GM TH700R4 & 4L60E Transmission - Novak Conversions
'There are three main castings of the 700R case. One is the standard car version. Another is cast slightly thicker, designated as the "K" case, as purposed for many trucks. The occurance of case breakage is very uncommon and most individuals swapping the 700R-4 into a Jeep probably will not be benefitted by one over the other. A third, rarer version was the "60 degree" version, as discussed below.'