Yes they have changed, those old ones were built with 100psi pumps, and the vac motors were in air-series (one sucking behind the other), so there was only a single 1.5" stack pipe in the waste tank, and there is a good chance teh one you are referring to used 2 stage vac motors, I would call it a 100cfm machine. You can bet the heater is caked with detergent and scale, if it's even still installed.
Todays machine would be a 200cfm, dual stack, and have a 450psi pump, and heat.
For $1200 you could probably get a current brand new 100cfm/100psi machine, look at the Breeze or RL100 on
www.mytee.com