Production for the original GM small block V8 was 1955. Not a redesign. That was the first year for the GM small block V8. It was a 4.3 liter 265 ci pushrod engine.
The original GM Small Block (as we know it today as a Gen I) came on the scene in 1955, not 1920.
The small block has gone through major re-designs throughout its life. We are currently on the Gen IV engines. My Gen IV LS2 in my GTO not only revs higher (stock - 6600 vs. 6400) than my 1UZ...
With the right knowledge and combination of parts an LSx will rev easily and happily to 7k rpm with a flat torque curve. And with the right gearing and double overdrive 6-speed can sip fuel to the tune of 30mpg on the highway.
Sounds like you had a bad one.
Its a hell of a swap and one of the...