Clustering and/or Hyper-V replica?

I would recommend you to use your old hardware in another way. I would purchase a new Dell server with the similar specs and create a Highly Available cluster. You can take a look at StarWind Virtual SAN that, as I know, can provide you with Highly Available storage. You will be able to create a redundant cluster with two nodes. As another option, you could take a look at what HPE offers.

Few words about Hyper-V Replica as it's one of the most frequently deployed scenarios.

You can PowerShell automate Hyper-V Replica no problem!

https://blogs.technet.microsoft.com/keithmayer/2012/10/05/automated-disaster-recovery-testing-and-failover-with-hyper-v-replica-and-powershell-3-0-for-free/

There are some caveats however:

1) There's no protection against a brain split, so you might want to run your orchestration site somewhere.

https://docs.microsoft.com/en-us/azure/site-recovery/site-recovery-faq

2) Hyper-V replica in a pre-WS2016 brings in a 2x write amplification gap. WS2016 is OK and third-party software using own changed block tracker, think of Veeam and StorageCraft don't have this issue.

https://forums.veeam.com/microsoft-hyper-v-f25/hyper-v-2012-r2-replica-vs-veeam-off-host-replication-t16374.html

3) There's some data loss on Hyper-V Replica failover and some downtime. You may be OK with them and maybe not, it's up to you completely!

https://redmondmag.com/articles/2014/12/01/hyperv-replica-for-disaster-recovery.aspx

Think about your RTO and RPP #s and your budget before you move on with your implementation.

A Hyper-V Failover Cluster will afford you automatic failover and failback in the event of a host failure. This requires shared storage between the cluster nodes.

Hyper-V Replica affords you manual failover and failback in the event of a host failure and doesn't require shared storage.

It's really a matter of what your budget will allow and what type of failover you require.