The thing you really need for good ALGOL code generation is a target architecture designed
to support it. All of the early implementations I know about that attempted full support
of ALGOL-60 targeted a virtual machine at run time. The outstanding counter-example, of
course, are the Burroughs B5000/6000/7000 stack machines, later known as Unisys A Series,
and currently still being marketed and supported by Unisys as their ClearPath MCP line.
The B5000 was designed in the early '60s, with first customer delivery on 1 April
1963. The ALGOL code generation was good enough (from a one-pass compiler, no less) that
it became the assembly language. There never was an assembler that ran on those systems,
although there was a basic assembler (termed OSIL) for it that ran on the older Burroughs
220 and was used to bootstrap early versions of the ALGOL compiler and OS. Once ALGOL
could compile itself, OSIL was abandoned.
The Burroughs ALGOL dialect is heavily extended, but at its core it was still a quite
complete implementation of Revised ALGOL-60.