I have a prefabricated fireplace, Superior Fireplace Model# CF3860. It's old and was installed when my house was built in the 80s. They are out of business and I can't find the manual online anywhere for this model. I want to run a gas line and install ventless gas logs. Anyone know if I can put ventless gas logs in this model? Everywhere I read either says to confirm it with the manual (can't find), or that it's ok to install them in a prefabricated unit.