The early Shoptasks only had 1.5" travel on the tailstock. Be careful about cutting off the ends of your tooling, because they need to be long enough to bottom out and self eject when retracting the barrel. The later models had a much longer travel- about 7", but they have a completely different casting.
A quick solution is to drill a hole through the base of the tailstock and tap a corresponding hole in the main carriage. Then you can run a long bolt through the tailstock base and thread it into the carriage. Then you just use the X axis feed to move the carriage and entire tailstock at one time- this will give you all the travel you need and it can also be done under power feed.