For those wondering about the fill-pipe test and not having a restrictor...this no longer applies in California as part of the bi-annual testing. Direct from the Bureau of Automotive Repair "Inspection Manual".
Another option is modify your stock fill pipe with a side inlet to fill the second tank. That is what I did my saddle tank.
I had a muffler shop bend the correct size pipe, measured and marked the stock fill pipe, fit and welded the two pieces together. Took about an hour and cost me $15.00 for the bent pipe and I welded it. I also removed the restrictor at the same time, then had it replated for $25.00.
I fill the stock tank as normal, and insert the nozzle towards the rear and down for the saddle tank. Have been using this for many years with no issue on my diesel swaped 60.
Pictures are kind of hard to see and these were taken before plating. Sorry, I did not take any before it was installed.