km144 case/bellhousing swap 5speed guts in a 4 speed?

As per the title, I M wording if anyone has done this, and kept records of it. I would like to take the 2 tranmssions I have and make
narrow block 5 speed out of the narrow km144 and wide km145. I am honestly just assuming the 5 speed is the km145 but from won't I can
tell the bellhousings don't separate from the rest of the case.

I read through a few threads and found a little bit of info by someone doing a rebuild, but many of the images don't seem to load right,
Probably because of age.

I do a fair bit of highway driving and I would like to keep the rpms below the 3500 that the 4 speed runs at high speeds. Before the 2.6
did the 2.6 thing and cracked its head and totally locked up, I liked the gearing and rpm that the 5 speed ran at. Short of changing front
and rear differentials, it seems that just getting one more gear would be easier.

Input is appreciated,
Thank you,
Dustin