I ran into similar factors many, many moons ago when I did my second "non-stock" engine swap (#1: Corvair into VW): Toyota engine + trans into '64 Triumph Spitfire.
For one thing, that rear axle ratio was extremely high, so even though the Toyota 5-speed trans had a decent top gear ratio, I always wanted to reach for "another" gear when it was transplanted into the much lighter, smaller, more aero Triumph.
There wasn't room for really big tires, but I went oversize as much as possible, which must have helped a tiny increment, but was still woefully inadequate.
Then there was the wimpiness of the Triumph rear end itself. Even though I didn't engage in hooliganism, I found myself sourcing and replacing twisted-off stub axles from the crap Triumph diff.
I found that I didn't enjoy that job, and dreamt of putting the Toyota rear axle in there, but that would have required major surgery i.e. frame, pan, and body... and it was becoming clear to me that the Spitfire, in spite of it's sexy styling, was a P.O.S.