The Featherlite Vantare H3-45's have never been Prevost-Factory slides. Also, around 2002 model vehicles, Featherlite Vantare went away from the HWH hydraulic mechanisms to twin electric motors driving the I-beams and controlled by their own PLC setup. The locks went to linear actuators rather than the hydraulic lock pins as well. The seal setup is the same as Diane's double-D seal, compressed when both fully out and fully in (i.e. no aircraft inflating seal).
If the shell is a pre-2004, the other big advantage is that you have a "non-egr" Series 60 engine, the best years as I am told, being 1996-2002 engine year. Best fuel efficiency, best reliability, most power, etc. All these are based on the years of customer feedback and driving them to shows across the country myself. Feel free to jump in with comments anyone lol. From customer feedback, it seems that Detroit Diesel had issues with turbos, etc on the EGR engines in the 2004-2007 Prevost shells (actually 03-06 engine dates, as Prevost always bought engines up a year in advance to allow for EPA changes/engineering time to implement the changes).