Impeller hub length for torque converter

My vehicle listed above is an Express 3500. recently has stopped locking the torque converter when cruising. And it started jerk into every gear as if it were a manual transmission and I had dumped the clutch. After researching it, the jerking into each gear is a result of the P0894 Transmission Component Slipping code. After thoroughly inspecting it, I found that the transmission cross member is covered in ATF coming from the top vent. This leads me to believe that the torque converter has overheated and spit all its fluid out.

I am looking at buying an aftermarket torque converter from Summit Racing with a high stall for better pickup off the line. https://www.summitracing.com/parts/ape-49482.
My dilemma is that I cannot determine whether the stock torque converter uses a 2" or 2.5" impeller hub. So I cannot order it until I can figure this out. Please, I need to figure this out before it causes actual damage to the transmission.

Thank you for taking the time to read this,
Conrad