After I purchased the line from ebay, i had to look around for an LTE phone in order to get the SIM card and upgrade the line to 4G LTE. I ended up purchasing a Pantech Breakout from ebay, which is probably the cheapest LTE phone you can get. Then, I went to the Verizon store, had them give me a SIM card, and activate the phone. From there, I cut down the SIM card using the stock micro SIM from the ipad as a template and switched the newly cut SIM with the stock micro SIM. At last, I have unlimited data on my iPad.
Note 1: Since I still have to pay for the voice + data, I made sure to enable call forwarding from the verizon number onto my ATT iPhone 4S.
Note 2: Instead of having to purchase an LTE phone like I did, I've heard that some people were successful with buying a micro SIM from ebay, calling verizon, and haven't them activate just the micro SIM without the phone. I found all of this out after I had already purchased the phone.