The motor in my 96 T/A is tired. I found a 95 Road Master with 42K on the clock
and it runs like a new. How well will it perform compared to a fresh F-Body motor?

Will it run 13's stock?

 

Less HP, heavy iron heads that flow more than the aluminum heads but do not permit aggressive ignition advance, lower compression ratio, smaller cam spec'd to provide low end grunt for a much heavier car but not as much top end. Probably pull off the line as well as the F-Body version, and run out of steam at high RPM.