I smoothed my firewall and I bought the main Gen IV unit so I could get it mocked up inside first. I ended up welding bolts to the inside of the firewall and plan on painting my firewall before the rest of the car. I did this so it wouldn't wreck the paint. I'm not using any bulkheads so I just drilled 4 1" holes for grommets. I'm going to run the hoses through the holes. I also bought the controls ( I went with the 3 nob electric one) so when I build the custom console, I have it.
I would recommend calling Frank at
www.gpsuperstore.com and talk to him. He knows alot about the Vintage Air kits and will sell it to you in stages. That's what he did with me.
Here's a pic of mine with the 4 holes I was talking about
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