Would it be worth it to just focus on the one compressor head and get that finalized and working?
Then worry about the other compressor head another time?
How large are your air needs right now? I think it would be worth it to have just some air, than to keep waiting on the full solution.....
Then add more air capacity as you need it....
I will say, I have the Lowes 60 gal 3.7hp air compressor and it has kept up with my needs quite well. I can run a cut off wheel or a die grinder continuously and it will keep up. I have not added a sand blaster to the shop yet. If or when I do, then I'll re-evaluate my needs and add air if needed.
Remember, sometimes good enough, is good enough. I know the OCD kicks in and you want it perfect, but really, sometimes the definition of perfect is that it works, not that it needs to look beautiful.......
I'm currently building a phase converter from some parts I bought off craigslist. I initially just rigged it up to test all the parts and that worked. Now I'm dragging along on getting the parts together to make it "perfect".... I fab'd a small frame for the motor to sit on. The wheels it is on are casters from Target for the metal-wire racks. They are sufficient, not overkill, but more than adequate--and they were only $15 for the set of four. I then bought a couple of new boxes for a term panel and outlets to sit in... I still need to pop the holes in the boxes and get some fitting to match everything together.... I just need to do it, but other projects keep cropping up.....

So I understand the pain, but sometimes, we just need to get it working (just good enough) so we can enjoy using the machines that we have......
Keep your chin up....