I asked around in the Zilog Z-80 DIY Facebook group and got some great feedback on the best choice for toolchain for Z80 C and ASM. I settled on z88dk. It's a bit complicated to get it set up but it does work well. It's command line driven and has a lot of options that have to be set.

The Target: Embedded_Z80 webpage was very helpful in figuring out command line options. I was able to compile a very simple program and get it running.

void main(void)
{
  while(1);
}

 The business end of the code compiled to:

244   0000              _main:
245   0000              l_main_00102:
246   0000  18 FE       	jr	l_main_00102

 When I ran the code the oscilloscope connected to the Output Enable line of the SRAM showed that there were three accesses to addresses 0, 1 and 2 which is what I expected.

MREQ* (top) and CPUCLK (bottom). Looks good.

Propagation delay from the PSoC logic. MREQ* on the bottom, SRAMOE* on the top. Less than 20 nS. Comparable to LSTTL speeds "in the day".

So far, so good.

Next task is getting some I/O emulation running. 

Perhaps start with a single 1-bit register connected to an LED? Need some Output to I/O space code to make that work.