I had tried a couple places and finally settled on Year One because they had the correct 2 1/2" thick core. The biggest problem I had was getting the pipes to fit through the firewall holes since the core is mounted firmly in the heater box. I ended up reaming the holes to almost twice the dia. to persuade the unit in without bending the pipes. Luckily, the gasket on the firewall was large enough to still cover opening once in place. Now, I've got carpet to replace but right now floor matts do the job!