The 225/50R16 size was discontinued over a year ago, so finding a new set will be tough. The only 16" size left is 245/50R16 which might not work on a 6.5" slicer.
Anyways, I have a set of 225's and here's my take on them. They are an excellent tire at the drag strip. Especially if the track is well prepped with traction compound. Even with a 75 shot of nitrous I was hard pressed to break them loose in first gear. Once you do your burnout, the tread turns into a sticky goo and the tires grip like crazy. But without the burnout, it acts like a regular tire. So using these on the street is kinda pointless. Plus the treadwear is only rated for about 15000 miles of normal driving.
One word of caution though, these tires can actually be too good! I only made about6 passes before snapping an axle in half. So they really put alot of stress on your driveline. I'd recommend carrying a set of spare axles or get a set of stage 5 axles from SHOnut($800). A quaife diff is also a must, I can't imaging the stocker taking too much of this kind of abuse. Motor mounts and your clutch should also be a concern.
So Nitto drag radials work very good, but the rest of your car has to be up to the task of racing with them.