Master cylinder upgrade question - 1990 Suburban V1500

[dsy1]

I have read a lot about the master cylinder upgrade from OBS to NBS to solve the common spongy brake feel. I decided to try this on my 1990 4WD Suburban (V1500) with front disc, rear drum, and rear anti-lock system. This '90 Suburban still has the '73-'87 body style. My original master cylinder looks like this one


The replacement was this one
.

This replacement did not fit under the hood (too tall). Is there another replacement master cylinder that will work, or a better solution? I have already tried a new original style master cylinder, changed to performance pads and rotors with braided lines in front, and new shoes in the rear, and power bled everything but still have soft brakes and a spongy feel.