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.

[v30crewcab]

a 1991 k1500 has a larger master cyl option that may work. yours is 1.14 stock size, the k1500 has a 1.41 size option.
the other option is a 1996 g30, has a 1.57 size master, but has a smaller reservoir in the front to fit under the van hood.
I'm assuming you don't have hydroboost?