How old is old? Back then in 2010± there were sometimes driver version dependencies, such that not every combination compiled with every new kernel. As far as I remember, the wanpipe drivers were always compiled against a specific kernel version.
In you case, you probably need a extra machine for testing to see what works. A newer card may be the better and less expensive approach. Depending on how the analog lines are used, an ATA gateway may be the easiest solution.