Recommend me a converter for this 273 - 727 combo

Update

I looked up the numbers on my 727 trans and its: PK3681862 245065583
I found info through this page: http://www.mymopar.com/downloads/transguide.pdf

It is infact from 74-75 727 and Hvy Duty, whatever that means?

So I know alteast that it is a 24 spline input shaft and that leads me to belive that the engine have the large torque converter register. Or have you ever heard of a combo of a 74-75 727 bolt up to a 1965 273 with the smaller register?