RTAI vs PREEMT_RT

you may just install it and see if you get lucky
if you troble findindg the parport just get the partition cleand and start over with RTAI

Ok , I try to install it and I come back to inform that is ok or not

It does work with both kernels, and if the computer is any good it will work nicely, albeit with a bit slower base thread.
Have 2 or 3 machines working with that setup for quite some time without a issues on some core2duo Dell optiplex SFF.

Depending on the hardware - rt_preempt does pretty good with printer port step gen....