In all honesty, the B377 was not a commercial failure. The aircraft did it's thing and did it well. It made decent profits in operation, and flew for over a decade for commercial operators. In fact, one B377 survives today - the Pregnant Guppy (the NASA Guppy is a KC-97 conversion). The only "failure" of the B377 was that it was a victim of the jet age. It could fly as far as an L-1649 even though the Guppy was slightly slower (only by about 10-15 knots), but neither was any match for the Comet, 707, or DC-8. It was no less reliable than the Starliner or it's earlier cousins, but both encountered the jet wall.
Also, to call it a "bomber conversion" is a misnomer. The only common item between the B-50 and the B377 is the wings, and even then, they aren't identical. The B-377 had all new landing gear (stronger), tail, inner wings, and fuselage. It also used a different model of R4360 than the B-50 which put out a couple hundred more horsepower than the B-50's R4360s did. More accurate would be that the numerically successful KC-97 and C-97 were conversions/modifications of the B377 where the B377 used the B-50 as merely a "starting point".
it would be nice to have some airliners in different configurations instead of the engine under the wing conventional one. it this really the most efficient way or has it just become the convention. I know the delta has some issues with AOA and such at low speeds. but why don't wee see airlines with the Canard design similar to the beech craft starship.