How about a Universal PCIe x 16_3 slot? After you guys answered I realized that if I put the modem in the first PCI slot it would block a fan connector, and if I put it in the second PCI slot if would be right in the smack middle of my graphics card fan.
The Universal slot is all the way at the bottom and would be a good fit. However, if not then its ok. I can just use a Molex adapter for my case fan and plug it into the PSU, and free up the first PCI slot.
You refer to a universal PCIe x16 and a universal PCI slot. What motherboard and what slot? If that was your question, you definitely can't install a PCI device in a PCIe slot. They are totally different and not compatible at all.