  Galaxy clusters have been found to host a range of diffuse, non-thermal
emission components, generally with steep, power law spectra. In this work we
report on the detection and follow-up of radio halos, relics, remnant radio
galaxies, and other fossil radio plasmas in Southern Sky galaxy clusters using
the Murchison Widefield Array and the Australian Square Kilometre Array
Pathfinder. We make use of the frequency coverage between the two radio
interferometers - from 88 to $\sim 900$ MHz - to characterise the integrated
spectra of these sources within this frequency range. Highlights from the
sample include the detection of a double relic system in Abell 3186, a
mini-halo in RXC J0137.2-0912, a candidate halo and relic in Abell 3399, and a
complex multi-episodic head-tail radio galaxy in Abell 3164. We compare this
selection of sources and candidates to the literature sample, finding sources
consistent with established radio power-cluster mass scaling relations.
Finally, we use the low-frequency integrated spectral index, $\alpha$ ($S_\nu
\propto \nu^\alpha$), of the detected sample of cluster remnants and fossil
sources to compare with samples of known halos, relics, remnants and fossils to
investigate a possible link between their electron populations. We find the
distributions of $\alpha$ to be consistent with relic and halo emission
generated by seed electrons that originated in fossil or remnant sources.
However, the present sample sizes are insufficient to rule out other scenarios.
